Trace DNA analysis: Do you know what your neighbour is doing?

Article Outline

• Abstract
• 1. Introduction
• 2. Results
  • 2.1. Section 1: crime scene examiners
    • 2.1.1. Crime scene examiners: training and experience
    • 2.1.2. Crime scene examiners: methods
      • 2.1.2.1. Fingerprinting
      • 2.1.2.2. DNA collection
    • 2.1.3. Crime scene examiners: contamination prevention
    • 2.1.4. Crime scene examiners: general practices
  • 2.2. Section 2: laboratory staff
    • 2.2.1. Laboratory staff: training and experience
    • 2.2.2. Laboratory staff: methods
      • 2.2.2.1. Sampling
      • 2.2.2.2. Extraction
      • 2.2.2.3. PCR
    • 2.2.3. Laboratory staff: contamination prevention
    • 2.2.4. Laboratory staff: analysis
    • 2.2.5. Laboratory staff: time and storage
    • 2.2.6. Laboratory staff: results
  • 2.3. Section 3: managers
    • 2.3.1. Managers: training and assessment
    • 2.3.2. Managers: methods and research
    • 2.3.3. Managers: results
• 3. Discussion
  • 3.1. Training and research
  • 3.2. Methods and processes
    • 3.2.1. Sampling
    • 3.2.2. Fingerprint examination
    • 3.2.3. Contamination prevention
    • 3.2.4. DNA analysis methods: extraction, amplification and analysis
    • 3.2.5. General practices
  • 3.3. Results and opinions
    • 3.3.1. Opinions of trace DNA evidence
• 4. Conclusions
• References
• Copyright

Abstract 

Since 1997 the analysis of DNA recovered from handled objects, or ‘trace’ DNA, has become routine and is frequently demanded from crime scene examinations. However, this analysis often produces unpredictable results. The factors affecting the recovery of full profiles are numerous, and include varying methods of collection and analysis.

Communication between forensic laboratories in Australia and New Zealand has been limited in the past, due in some part to sheer distance. Because of its relatively small population and low number of forensic jurisdictions this region is in an excellent position to provide a collective approach. However, the protocols, training methods and research of each jurisdiction had not been widely exchanged. A survey was developed to benchmark the current practices involved in trace DNA analysis, aiming to provide information for training programs and research directions, and to identify factors contributing to the success or failure of the analysis.

The survey was divided in to three target groups: crime scene officers, DNA laboratory scientists, and managers of these staff. In late 2004 surveys were sent to forensic organisations in every Australian jurisdiction and New Zealand. A total of 169 completed surveys were received with a return rate of 54%. Information was collated regarding sampling, extraction, amplification and analysis methods, contamination prevention, samples collected, success rates, personnel training and education, and concurrent fingerprinting.

The data from the survey responses provided an insight into aspects of trace DNA analysis, from crime scene to interpretation and management. Several concerning factors arose from the survey. Results collation is a significant issue being identified as poor and differing widely, preventing inter-jurisdictional comparison and intra-jurisdictional assessment of both the processes and outputs. A second point of note is the widespread lack of refresher training and proficiency testing, with no set standard for initial training courses. A common theme to these and other issues was the need for a collective approach to training and methodology in trace DNA analysis.

Trace DNA is a small fraction of the evidence available in current investigations, and parallels to these results and problems will no doubt be found in other forensic disciplines internationally. The significant point to be realised from this study is the need for effective communication lines between forensic organisations to ensure that best practice is followed, ideally with a cohesive pan-jurisdictional approach.

Keywords: Trace DNA, DNA profiling, Survey, Methods, Crime scene investigation, Forensic management

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1. Introduction 

In 1997, Australian researchers were the first to publish success obtaining DNA profiles from handled objects [1]. Since that time, the analysis of DNA from shed skin cells on handled surfaces, ‘trace’ or ‘contact’ DNA, has developed and become a routine class of biological evidence. In large cases, many hundreds of trace samples such as cartridge cases and weapons are submitted in the hope of retrieving a usable profile from the offender.

However, as demonstrated in casework and research, retrieving useable profiles from trace DNA exhibits is not guaranteed. There are numerous factors that affect the rate of recovery of full profiles, such as the ability of the individual to shed cells, the substrate surface, the time of contact and delay until analysis, and the environment [2], [3], [4], [5]. In addition to these external conditions, there are many varying methods used to collect, extract and analyse the samples, each with particular benefits and limitations [6], [7], [8], [9].

As technology becomes available to test for increasingly minute amounts of DNA, accuracy in sampling, analysis and contamination prevention become vitally important. Despite this, there has been little attempt to survey exactly which methods and practices are being employed across the different laboratories in the Australia and New Zealand region. Communication between laboratories is often limited due to the large distances between laboratories and their organisational independence. A review to benchmark the methods and protocols of trace DNA analysis in the Australian and New Zealand forensic laboratories has never been conducted. Indeed it is difficult to find such surveys from throughout the international forensic community. In our own work we have identified this knowledge gap, and in conjunction with representative authorities developed a survey to collate this data. The survey was constructed to take into account the non-sample related aspects that may affect the chance of DNA recovery, by investigating the process from sample collection to profile reporting. The survey focused solely on trace DNA and the relevant methods involved, and not those for DNA from blood or semen.

The survey aimed to benchmark the current practices employed in trace DNA analysis, to identify factors contributing to the success or failure of the analysis, and to provide information for training programs and research directions. It was envisaged that the results would initiate much needed discussion amongst stakeholder organisations, and provide data to support or refute circulating anecdotal information.

The survey was divided according to three target groups of forensic practitioners: crime scene officers, DNA laboratory scientists, and managers of these staff. A separate survey was developed according to the types of duties each group might perform. Each survey contained short answer and ‘tick a box’ type questions calling for information about the methods an individual might use, their opinions on the methods and results, and details about their training and education. Managers were asked to comment on the methods used by their staff, the results their laboratory obtains and the training and education provided to and required of their staff.

The surveys were distributed to individuals from 12 forensic organisations in Australia and New Zealand between September and December 2004. The number of respondents varied considerably between jurisdictions, but was approximately proportional to the relative populations of those jurisdictions.

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2. Results 

A total of 169 completed surveys were received; 92 Section 1 (Crime scene), 58 Section 2 (Laboratory scientists) and 19 Section 3 (Managers). The overall return rate was 54%. For the sake of brevity, not all results have been included here. The additional data may be obtained from the corresponding author.

2.1. Section 1: crime scene examiners 

Crime scene examiners are the most diverse group surveyed. It is evident from the returned surveys that jurisdictions have widely different procedures in terms of their personnel response to crime scenes. The examiners vary in terms of their employment status (police or civilian), duties (either solely fingerprint examiners, physical evidence/photography or both) and types of crime examined (volume/minor crime only, major crime only, or both). Of the 92 crime scene examiners who responded, 56 (60%) were sworn police officers and 26 (40%) were un-sworn civilian employees.

The majority (56%) of the responding crime scene examiners did not hold a university degree (Fig. 1). 77% of respondents had been employed as crime scene examiners for more than 2 years, 46% for more than 5 years. For over half (60%) of the respondents it had been 2 or more years since their original training in trace DNA evidence identification and collection. Two respondents stated they were not officially provided training on trace DNA evidence.

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• Fig. 1. 

  Highest education level of respondents, crime scene examiners vs. Laboratory staff.

The format of trace DNA training varied both within and between jurisdictions. 16% of crime scene examiners surveyed suggested their training was one-on-one, 23% were part of a group tutorial, and 34% attended lectures and participated in practical exercises. The remainder had some combination of these methods. It was noted that respondents within the same jurisdiction gave different answers, suggesting either that training methods changed in format over time, or that the training methodology was informal, leading to various interpretations of the format.

The length and method of assessment of the course varied considerably. 41% were provided with 1–2h of training in trace DNA evidence, whereas 20% attended a day-long course. A half-day course and a weeklong course were the next most common responses, with 16% and 11% of respondents, respectively. In terms of assessment, 39% of examiners were given a practical test and 13% were given both practical and written tests. 33% were not formally assessed in trace DNA evidence.

Respondents were asked if refresher courses in trace DNA evidence were provided by their organisation. A majority (70%) stated that refresher courses were not provided. Of the remainder, 19% were given yearly updates, and for 10% updates were given more than one year apart.

2.1.2.1. Fingerprinting 

Standard fingerprint powder (black carbon and titanium white) is by far the most common fingerprint development method used at crime scenes (92%), and consequently squirrel hair brushes are the most common applicator used (84%). These applicators are kept in use by officers generally for 6 months or longer (95%), and are only occasionally cleaned (54%), if at all, with 41% stating they never cleaned applicators.

2.1.2.2. DNA collection 

The methods used by crime scene examiners to collect trace DNA are shown in Fig. 2. 56% of respondents used more than one method for trace DNA collection. The most common solution used during swabbing was sterile water (86%), 7% of examiners use a concentration of ethanol, and 7% use water or ethanol. The cotton swab is by far the most popular type of swab (82%), followed by foam and branded swabs (11% and 5%, respectively).

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• Fig. 2. 

  DNA collection methods: crime scene examiners vs. laboratory staff.

Most scene examiners store their exhibits at room temperature (72%), with around a third refrigerating samples. 79% of examiners stated they would submit exhibits to a laboratory within a week of their collection, and 13% within 1 day. 15% take more than 2 weeks to convey their exhibits.

Questions regarding the wearing of gloves, facemasks and other body protection during fingerprint and trace DNA collection were asked of examiners.

Reassuringly, the majority of examiners wore gloves during fingerprint examination (90%) and DNA collection (99%). However, the regularity that those gloves were changed varied somewhat. Table 1, Table 2 detail what type of gloves are used, and how often examiners changed their gloves. Facemasks are not worn as regularly as gloves, with 19% of scene examiners stating they never wear a mask during a DNA examination (Table 2). Again, the frequency that facemasks are changed varies considerably, from per exhibit to weekly or monthly.

Table 1. Crime scene examiners: contamination prevention during fingerprint examinations

Table 2. Contamination prevention during DNA sampling: laboratory (lab) staff vs. crime scene investigators (CSIs)

43% of examiners said they wear no other body covering other than their standard work wear. 31% stated they wore overalls, and 6% another type of full body covering. Only 4% professed to wear hairnets.

The majority (73%) of examiners collect five or fewer trace DNA samples per week, however, 5% collect more than 20 trace DNA samples every week. The most common items submitted for trace DNA analysis were food and drink related items, vehicle swabs, and clothing (data not shown).

2.2. Section 2: laboratory staff 

Staff employed in forensic DNA laboratories are generally divided into two broad categories: ‘Biologists’, who examine the sample after its receipt, determine what methods are to be employed, interpret and ‘report’ the results (produce statements for court), and ‘Technicians’, who perform the extraction, amplification and analysis steps, without any interpretation or reporting. In the main, biologists have more experience than technicians. There are slight variations in the roles of these two categories between jurisdictions, or duties may be merged in some areas.

All respondents to this section of the survey were civilians. Forensic laboratories in the Australia and New Zealand region are most commonly government run. Four jurisdictions have the DNA laboratory as a division of the police service, employing civilian scientists. In the remaining five jurisdictions the laboratories are separate organisations to the police. Of these, four are run by the state health department, and the fifth is a semi-private entity.

As evident in Fig. 1, a large percentage of laboratory staff have an undergraduate or higher degree (93%). 40% of laboratory scientists have post-graduate qualifications. The type of degree laboratory scientists hold varies, with the most common type found to be a degree majoring in molecular biology and genetics (47%).

22% of laboratory staff have been employed for more than 5 years, 60% between 1 and 5 years, leaving 18% of staff with under 1 year experience.

Fig. 3 shows the comparison between the level of experience in crime scene examiners and laboratory staff. Crime scene examiners were found to have more experience than laboratory staff, with 78% of DNA laboratory staff having less than 5 years experience. This is to be expected given the considerable increase in the workload of DNA laboratories in recent years, and the subsequent large recruitment of staff.

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• Fig. 3. 

  Comparison in experience of crime scene examiners and DNA laboratory staff.

59% of respondents stated it had been more than 2 years since their initial training in trace DNA analysis. The length of this training was stated to be greater than a week in the majority of cases (43%), the next most common response was for a half-day course or shorter (32%). The most common formats for the training was one-on-one (56%), and practical demonstration (32%). The requirement for assessment was equally divided between those who were not assessed in trace DNA analysis (42%), and those who undertook a practical test (41%). 92% of laboratory staff have never received a refresher course in trace DNA analysis.

2.2.2.1. Sampling 

The various types of sampling methods employed by laboratory staff are listed in Fig. 2. Tapelifting and wet and dry swabbing were the two most common sampling methods used. All respondents use more than one method of sampling. Cotton swabs were by far the most common type used (67%), and 13% of laboratory staff use a combination of cotton, foam or branded swabs. The majority (70%) use sterile water as a swabbing solution, and 15% use a solution of ethanol.

2.2.2.2. Extraction 

Standard chelex and organic extraction methods were equally the most common extraction methods used (33% each). 18% of respondents stated they use both chelex and organic methods, and 13% use solutions of 20% chelex. 37% of laboratory staff stated they would always use a clean-up method during extraction. 63% stated some type of variation is permitted in their standard extraction procedures, generally adding an additional step or varying reagent volumes to suit the sample.

2.2.2.3. PCR 

Profiler Plus is the most common PCR kit used in forensic laboratories in the Australia and New Zealand region, and 92% of respondents use 28 PCR cycles for amplification. Only one jurisdiction (New Zealand) uses SGM+, and a minority of respondents (12%) stated they use Profiler Plus and Cofiler or Identifiler. 88% of responding laboratory staff stated they are not permitted any variation in their PCR protocol. Of the four positive responses, these individuals were allowed to vary cycle number (two responses, stating this would occur vary rarely), reaction volume, or whether bovine serum albumin (BSA) was added.

A minority of laboratory staff had employed low-copy number (LCN) analysis (28%), however, most are aware of the technology (86%). Given the limited number of respondents permitted to vary cycle number in casework, it is assumed that those with experience in LCN analysis had used it in research only.

In addition to specific methods used, participants were asked what contamination prevention measures they take during sampling and extraction. As would be expected, all of the respondents stated they wore gloves during sampling and extraction, most commonly one pair of latex gloves (Table 2, Table 3). During sampling, these gloves are changed at least once per exhibit (98%). The number of times gloves are changed during extraction varied from a time period of 15–30min, or after touching something outside the extraction process, or other variables.

Table 3. Laboratory staff: glove and facemask usage during DNA extraction

DNA extraction
Type gloves	%	Changed	%	Facemask	%	Changed	%
Latex	95	15mins	10	Always worn	48	Per batch	35
2 pairs latex	5	30mins	7	Spec cond only	14	When exit lab	4
		When exit lab	2	Never worn	36	Daily	46
		Per batch	2			Weekly	8
		After touching	17			Other/varies	8
		Other/varies	62

Facemasks are worn less often than gloves, during both sampling (80% of respondents) and extraction (48%), as shown in Table 2, Table 3. Some of the respondents stated they wear facemasks for specific conditions only, such as odorous samples. Facemasks are most often changed daily for both sampling (48%) and extraction (46%).

Hairnets are not often worn, according to the responses (data not shown). 33% wear hairnets during sampling and none stated they wear hairnets during extraction procedures.

Peak heights were the major criteria for calling alleles (52%), with 21% also considering the morphology of the peak. The minimum height limit for calling heterozygote alleles varied between 50rfu (54%), 100rfu (22%), and 150rfu (3%). The remaining respondents stated their limits varied depending on the circumstances. For homozygote alleles, the calling limit ranged amongst 200rfu (38%), 250rfu (30%), 300rfu (20%) and 400rfu (3%).

The average time periods taken between each step of sample analysis, from the time a sample is booked in to the laboratory through to the typing of the sample, are shown in Fig. 4. Respondents commented that these times were averages only, and that cases are expedited when requested.

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• Fig. 4. 

  Laboratory staff: time periods between analysis steps.

Laboratory staff was also asked about sample storage conditions at each stage of analysis. Exhibits were mainly kept at room temperature on receipt at the laboratory (47%), however, an equal percentage stated that this varied depending on the needs of the sample. The majority stated that pre- and post-amplification extracts were stored in the refrigerator (87% and 82%, respectively). 63% of respondents indicated that post-amplification products were stored in a freezer at −15°C or cooler, as were 75% of post-genotyping products.

The majority (69%) of laboratory staff indicated that they personally process less than 20 trace DNA samples per week, and 7% would process in excess of 50 samples. Laboratory staff were asked to estimate the proportion of the trace samples processed which provide a result suitable for entry onto their DNA database, or that is of use to investigators through intelligence links. Over half (52%) estimated the overall success rate of trace samples to be between 25 and 50%. 45% of respondents were more conservative with an estimate of between 10 and 25%. Laboratory staff also estimated success rates for different trace DNA sample types, with rough estimates suggesting trace swabs of food and drink items, clothing items and personal effects produced more useful profiles (Fig. 5). Whilst the survey asked participants to consider only the trace aspects of food and drink items (for example the handled area rather than the mouth of a drink container), it is possible that respondents may have taken into account saliva samples in their estimates.

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• Fig. 5. 

  Estimates of success rates^* of different sample types: laboratory staff vs. managers (^*Percentage of samples deemed to provide a result that is suitable for use in the particular case or for inclusion on the DNA database ^**Personal effects=watches, jewellery, reading glasses, sunglasses, shoes, belts.)

2.3. Section 3: managers 

Of the 19 surveys received from managers, six were from managers of crime scene sections, two from fingerprint sections, and 11 from DNA laboratories. The number of staff supervised by each manager was fairly evenly spread from less than 10 staff to more than 40 (Table 4). The number of staff under the manager who are trained to collect trace DNA ranged similarly. The number of staff trained to analyse or interpret trace DNA was lower, however, with 53% having no staff trained in these procedures.

Table 4. Managers: staff numbers and duties

From the managers’ responses, the minimum level of education required for staff at these organisations was most commonly an undergraduate degree (50%). However, 39% of managers stated a university degree is not a pre-requisite for employment in their organisation.

Mangers were asked as to the type of training in trace DNA analysis or collection their organisation provided to staff. The majority (64%) responded that they gave ‘on the job’ training only, with the remainder providing a course, lectures or tutorials. Refresher courses in trace DNA analysis are only occasionally conducted (32%), or in a response to specific needs (53%). 16% of managers stated refresher courses in trace DNA are never conducted in their organisation.

Proficiency testing in trace DNA is also rarely conducted. 84% (n=19) of the organisations never undertake proficiency testing specifically including trace DNA analysis, according to the responding managers.

The questions for this section of the survey were relevant for managers of DNA laboratories only, and were not answered by fingerprint or crime scene section managers.

Managers were asked if their staff are permitted to vary any methods used in trace DNA analysis. Four responded yes, four only on rare occasions or limited circumstances, and four are not permitted any variation.

The survey found that not all laboratories were conducting research into alternative procedures or methods in each step of trace DNA analysis. Of the 11 responding managers of DNA laboratories, the most common research topics were extraction and typing or interpretation methods (five and four responses, respectively), followed by sampling methods and Low Copy Number techniques (each with three responses).

Managers were asked if they kept statistical records at the various stages of trace DNA analysis. 35% collected statistics on the type and number of samples that had been submitted to the laboratory, and nearly half collected statistics on the number of these samples submitted for DNA extraction. Only two respondents stated they kept a record of the number of samples able to be amplified. 35% kept records of the amount of samples which resulted in full or partial profiles.

The number of trace samples analysed per week by the managers’ sections ranged from none (four responses) to more than 50 (four responses). The percentage of all items tested that were trace DNA samples was most commonly between 10 and 50% (eight responses). Fig. 5 shows the estimated success rates managers attributed to different sample types.

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3. Discussion 

3.1. Training and research 

The finding that laboratory staff have higher background levels of education than crime scene examiners was expected (Fig. 1), given the tradition of on-the-job training of police officers into forensics and scene examination roles. Currently, several jurisdictions in the region are recruiting crime scene examiners with science degrees, whilst in others the reverse is occurring, with scene examiners being recruited from police ranks with little to no emphasis on scientific background. It may be of interest to track the effect (if any) of these differing recruitment policies on the quality of evidence and results.

30–40% of scene examiners and laboratory staff had not been formally assessed in trace DNA collection or analysis. Evaluation of some kind is an important component of training courses to ensure correct concepts and techniques have been absorbed by participants. Given the large percentages of junior staff in DNA laboratories, effective training and assessment would seem to be crucial. However, an alternative point of view is that the newer staff would have a good theoretical grounding in the latest techniques, given the fast progression of the molecular biology field, and it is actually the ‘more experienced’ staff that lack a formal education in DNA methodology and thus require more training.

Equally concerning as the lack of formal initial training courses is the absence of regular refresher training and proficiency testing. Refresher courses are in the majority only conducted in specific circumstances, and proficiency testing is generally not conducted specifically towards trace DNA. DNA analysis is a constantly changing field and it would seem that keeping staff abreast of the latest developments would be of benefit to employers. In addition, the move towards analysing lower levels of DNA demands that the analysts are accurate and precise in trace DNA analysis. Ongoing training and education also provides for a much higher job satisfaction and employee loyalty, in an age where technology has allowed analyses to be robotic and repetitive.

A difference in perception of training between the managers and their staff was noted, for both crime scene and laboratory scientists. 85% of managers suggested that refresher courses in trace DNA were conducted occasionally or in a response to specific need, however, 92% of laboratory staff stated they had never received a refresher course. From the responses of managers it appears that the approach to refresher courses is reactive, occurring only when a problem arises rather than as a preventative measure. An interesting discussion point is to consider who is responsible for refresher training—should the managers provide for this, or is the onus on the staff member to keep up-to-date with the latest research and methods? In either case, managers should ensure there are sufficient literary resources available and provide time for self-learning, even with obvious time and monetary constraints.

In response to the absence of proficiency testing, national bodies could develop and facilitate testing incorporating trace DNA analysis, rather than each laboratory developing separate standards and criteria. Given the random nature of trace DNA analysis, proficiency testing may be difficult to oversee, however, the benefits of having some mechanism to ensure that labs are analysing and interpreting in an acceptable manner warrants further investigation of this area. In the past proficiency testing has often been focussed on laboratory staff rather than scene examiners. It would be feasible to test examiners in their swabbing ability to ensure appropriate methodology is used and that the best possible results are achieved. Examiners who regularly give poor results from their casework swabs could be targeted for proficiency testing if laboratories were able to provide accurate statistics for each examiner. This level of results reporting is generally not possible at this stage, however, would be an extremely useful review tool.

Several managers stated that their laboratories were conducting research into various areas of DNA analysis, with extraction and typing/interpretation receiving the most attention. Few laboratories in the region are known to have specific research and development sections or personnel. It was interesting and encouraging to note that laboratories were able to conduct research despite many comments of overwork and lack of time. The benefits of operational laboratories conducting or collaborating in research are to ensure quality and efficiency of methods and results, to ensure that research is relevant and appropriate, and to provide staff with stimulating working conditions that encourage professional development. With the cost of staffing, reagents and instruments being so considerable, research and development is seen as a luxury rather than a necessity and consequently funding can be lean and sporadic. At present, research outcomes are passed on in an ad hoc manner, often by word of mouth between staff.

3.2. Methods and processes 

Similarities were observed between scene examiners and laboratory staff in terms of their sampling methods. Majorities of both groups stated they rotated swabs continually during swabbing, however, a third of scene examiners maintain swabs in a fixed position whilst swabbing, concentrating DNA onto one side. This method of swabbing is useful and effective for bloodstains, but is likely to be less so for invisible trace samples [10]. Laboratory staff are slightly more likely to swab for a longer time than scene examiners, with 27% passing the swab more than 10 times over the substrate as opposed to 21% of scene examiners. Brief swabbing of a surface may reduce the chance of successful profiling. Many crime scene examiners also suggest they use a single swab to collect trace DNA, even though it is known that a ‘wet and dry’ or multiple swabbing method will tend to retrieve more DNA [6], [10], [11], [12]. These results lend support to the need for more and/or better training, and for proficiency testing to identify examiners with poor technique.

Cotton swabs may be so prevalent for historical and/or financial reasons; however, there is limited research into their actual efficiency. Van Oorschot et al. [6] found that a significant proportion of DNA collected by a cotton swab is not retrieved during the extraction phase. Also, the brittle nature of wooden swab sticks may prevent examiners from swabbing with adequate pressure or for an appropriate length of time. There may be better methods or swabs available, and it is known that research projects are planned in some jurisdictions to test these. Likewise, other solvents such as dilute ethanol have been shown to produce better results than sterile water [9], [12], yet sterile water is still most commonly used. A collective approach to determine the most effective sampling method would seem beneficial.

The overwhelming majority of crime scene examiners around the region use squirrel hair brushes and standard black and white powders for fingerprint examinations. It is interesting that these methods have such wide appeal, given that in other countries metallic powders and zephyr or feather brushes are far more popular, and have been shown to have a less abrasive affect on fingerprint ridges [13], [14]. However, metallic and magnetic powders have shown to inhibit DNA analysis and quantitation methods [15], so it is conceivable that the widespread use of granular powders may be beneficial to trace DNA analysis. In either case, Van Oorschot et al. [6] found that powdered samples gave a 25% decline in the amount of DNA retrieved as compared to un-powdered samples. This could in part be due to the action of powdering which may remove DNA-containing material loosely adhered to the surface. Furthermore, the DNA extraction methodologies employed need to remove all powder, as it is known that its presence in the DNA extract can inhibit DNA amplification [6].

Another implication for trace DNA analysis in a legal context may be the length of time powder brushes are kept in use (over 6 months in 74% of cases), and how rarely they are cleaned. Whilst the risk is minimal, powder brushes have been shown to carry DNA with the potential for transfer between samples [16], [17]. As testing becomes more sensitive and as LCN analysis is becoming routine in other countries [18], the detection of transfer will increase and any potential for contamination should be considered. There is little research in to the effectiveness or appropriate methodology of brush cleaning (although such projects are in planning). Many of the jurisdictions have a division between the fingerprint and biology groups, which could create a knowledge gap and prevent efficient examinations when the evidence types overlap. A multi-jurisdictional multi-disciplinary discussion group into issues surrounding the combination of DNA and fingerprint evidence would be beneficial, leading to a collective approach to examinations and presentation of such evidence in court. The legal community is becoming more aware of issues surrounding trace DNA analysis, and many questions put to witnesses in court are difficult to answer without strong empirical research and cohesive organisational policy [19].

The contamination prevention procedures undertaken appear to be adequate in the most part. Gloves and masks are changed regularly during examinations. Scene and laboratory examiners generally wear additional protection such as overalls or lab coats. The measures taken by scene examiners during trace DNA sampling are comparable to those employed by laboratory scientists. Latex gloves are mostly worn, however, only 26% of scene examiners and 8% of laboratory staff wear two pairs during examinations. A concerning observation is that 19% of scene examiners ‘never’ wear facemasks during trace DNA sampling. 20% of laboratory staff only wear facemasks in certain situations, generally when a sample is malodorous. Only 4% of scene examiners and 49% of lab staff wear hairnets during examinations. The experiments conducted by Rutty et al. [20] demonstrate the contamination that can occur through the general movement, actions and conversation of an examiner when protective clothing is not worn during an examination.

The level of contamination prevention employed by scene examiners during fingerprint examination is considerably lower than that used during DNA sampling. Gloves worn during fingerprint examination may be kept in use for up to or beyond a week, and facemasks are only worn for specific situations (additional comments suggest this is usually to prevent inhalation of powder rather than prevent contamination). The survey did not question whether the fingerprint examination was undertaken after DNA sampling, and therefore caution would not be necessary. However, there is always a chance that an area or exhibit may be considered for DNA analysis in the future, and perhaps greater consideration is needed from fingerprint examiners.

As for sampling methods, intra-jurisdictional variation was observed in contamination prevention procedures, indicating that organisational policies have not been developed or are not enforced. Either methods were not demonstrated clearly in training, or proficiency testing has not corrected lapsed procedures. Whilst some variation in scene examination is necessary to allow for personal preferences and initiative, contamination prevention is one area where strict protocols are essential.

Specific methods used in these stages of analysis were difficult to ascertain, as protocols were not provided by the laboratories. Often sections were left blank regarding details such as precise volumes and times, or varied intra-laboratory, suggesting perhaps that staff did not know off-hand or did not refer to exact protocols.

‘Standard’ chelex and organic extraction methods were equally popular. The literature is also divided between extraction methods for trace DNA analysis. Of 51 research articles that investigate trace or saliva DNA analysis dating from 1991 to the present, 24 used chelex extraction and 22 organic. A recent article has suggested that simple chelex or buffer extraction methods are more effective than commercial kits, and are suitable for automation unlike organic protocols [21]. Incubation time varied little, with most incubating at 56°C for 30min and all at 100°C for 8min. Methods of incubation ranged from heatblocks to waterbaths and shaking waterbaths. Responses to vortex and centrifuge times and locations of these in the protocol were variable and difficult to group. Over a third of respondents stated they always used a clean-up method during or after extractions (Section 2.2.2). Unnecessary use of clean-up methods may result in a loss of valuable DNA in trace samples, and it may be worth investigating whether standard procedures decree that staff always employ clean-up procedures, or if each sample actually demanded it.

This leads into a discussion of the freedom (or lack of) given to staff in the variation of standard methods. Trace DNA samples are notoriously difficult to recover useable profiles from and it would be conceivable that some variation would be necessary to achieve results from the diverse conditions of the samples. 63% of laboratory staff (and at least one from every jurisdiction) were permitted to vary standard extraction procedures for difficult samples. The staff permitted variation did not hold higher education levels or have more experience than those who were not. Far fewer (12%) were permitted to vary standard amplification methods. Only a small proportion of lab staff are utilising extra cycles or other modifications to enhance their chance of acquiring a useful profile from trace samples (Section 2.2.2). It would be interesting to determine if better results could be achieved when scientists are permitted to apply their knowledge and training to analyses. If such freedom were to be allowed thorough training and assessment would of course be essential.

DNA analysis was generally found to be similar amongst laboratories. Discrepancies were found in details such at the injection volumes and run times. Minimum height limits for calling hetero- and homozygotes varied between the jurisdictions, but reassuringly not within each jurisdiction. An additional question could ask why these values are set at such, and the extent of validation undertaken to assess the limits. Setting high minimum levels may unnecessarily reduce the opportunity to generate informative profiles.

The delay from collection to laboratory submission varied amongst examiners, likewise the time for each analysis step amongst lab staff. Extensive delays in sample collection and/or extraction could limit recovery of high quality DNA. Many of the crime scene sections and laboratories responded that they do not have set protocols but would prioritise samples according to their seriousness. Taking the most common responses of laboratory scientists, on average the analysis of a sample is completed less than 3 weeks after its receipt. If the time taken from receipt of a sample to its extraction is discounted, the return time is much quicker again. It appears the analysis process is time efficient but the major delay is actually getting the sample to the analysis stage. This step is where staff use discretion to expedite urgent samples, and conversely delay samples from crime types with a perceived lesser value. The survey did not ask how long the reporting phase would take or the time for the result to actually reach investigators, which is often another limiting step.

3.3. Results and opinions 

There were differences in estimates of success rates for particular sample types amongst jurisdictions (data not shown). An aim of the survey was to identify possible reasons as to differences in success rates between the jurisdictions, and then to evaluate to what extent these differences are associated with the education and/or training received and the processes or methodologies used. However, this could not be measured precisely as laboratories either do not record statistics and results or do so in a manner that restricts the ability to cross-compare. Only one manager stated that their laboratory collected detailed statistics, with the majority collecting only ‘general’ or ‘some’ statistics. Several anecdotal comments suggest that laboratory scientists are left to collate statistics themselves rather than having dedicated administrative employees and/or do not have access to effective electronic laboratory information systems.

The issue of results collation needs to be rectified, as laboratories should be able to provide detailed results to their clients in order to ensure the efficiency and transparency of their service. As mentioned previously, having detailed statistics available could be used to identify training needs, assist sample targeting and help develop methods and policies for different sample types. Results collation and analysis and the ability to compare across jurisdictions would identify improvement opportunities, aid the direction of research and greatly assist laboratory managers in both their sample and staff management and quality of service.

High work-load was a recurring theme amongst the comments of respondents. It is apparent that such caseloads hinder data collection and process review. This in turn negatively affects customer service and the professional development and motivation of staff. This should be an important consideration for managers as they assess finances and resource requirements.

The estimated and actual success rates should improve with improvements in applied methodologies and training.

A final question in the survey was to ask respondents whether they thought trace DNA was highly significant, of average significance, or insignificant as evidence in criminal cases (Fig. 6).

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• Fig. 6. 

  Comparison between the opinion of respondents on the value or significance of trace DNA as evidence.

The regard in which trace DNA evidence is held as evidence in court cases was evenly divided between ‘average’ and ‘highly significant’. Crime scene examiners were the most cynical of the three groups, with several comments stating that trace DNA evidence was insignificant due to budget constraints that prevent such evidence being fully utilised. Several laboratory scientists and managers provided their own ‘depends’ category. These responders commented that trace DNA is highly significant in terms of its intelligence applications, but only mediocre if it is needed to be relied upon as evidence in court. This point of view demonstrates a paradigm shift in the way DNA is used in criminal cases. Because of its identifying power, DNA evidence has often been used as a crutch in investigations. As trace DNA often provides only partial profiles it can sometimes be discounted as useful evidence as it may not identify a specific offender. However, partial profiles can provide new lines of inquiry where there may be none, which with further investigation can lead to a successful result. It is positive that practitioners and managers are recognising this potentially valuable aspect of trace DNA evidence. As technology and procedures continue to improve, along with advancements in the understanding of the trace evidence characteristics (transfer, persistence) of DNA, this type of evidence will become more valuable to investigations in the future. More sophisticated interpretation methods are being developed to ease the explanation of trace DNA samples in court [22], [23].

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4. Conclusions 

The survey results provided a useful overview of the current state of trace DNA analysis (circa 2004) in Australia and New Zealand. Similarities were noted between sampling, examination and analysis methods. Issues identified include the lack of uniform training courses and proficiency testing, a lack of data gathering and uniform results reporting, and contamination prevention. The common theme is the need for an overseeing body to collate research and determine best practice in all areas of trace DNA analysis. The relatively small forensic community present in the region is in an excellent position to provide a cohesive approach, in that despite the large distances between organisations, members are aware of and have good relationships with their local colleagues. The results of the survey were disseminated to participants, and this has already triggered positive changes in assessing, revising and enforcing protocols as well as discussion amongst jurisdictions aimed at improving the collating and reporting of results.

These findings are likely to be echoed in other international jurisdictions. Conducting a similar audit of processes in neighbouring regions could highlight duplication of research, variances in contamination prevention, or more resourceful methods and procedures. The most important point to come from this survey, applicable to all areas and practitioners of forensic science, is the need for more benchmarking exercises and for clearer communication lines. Communication between forensic institutions (crime scene units and laboratories), both within and across disciplines, is fundamental to the provision of accurate and efficient examinations.

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