A Review of DNA Lab Requests from Municipal Departments and RCMP Detachments in the Lower Mainland of British Columbia (2006-2011)

3. General Sample Characteristics

In terms of the nature of the offences associated to the files reviewed (n = 581), a little more than half (59 percent) were associated to Break and Enter offences. Less than one-fifth of files were associated to a robbery (16 percent) and a slightly smaller proportion was classified as ‘other’ (9 percent).Footnote 3 Very few files were associated with a homicide (5 percent), an assault (3 percent), or a sexual assault (7 percent) (see Figure 1).

Figure 1: primary offence type (n = 581)

Figure 1 illustrates the nature of the offences associated with the file reviews on a bar graph.

Figure 1 - Text equivalent

Figure 1 illustrates the nature of the offences associated with the file reviews on a bar graph. A little more than half (59 percent) were associated to Break and Enter offences. Less than one-fifth of files were associated to a robbery (16 percent) and a slightly smaller proportion was classified as ‘other’ (9 percent). Very few files were associated with a homicide (5 percent), an assault (3 percent), a sexual assault (7 percent), or an ‘other’ property crime.

In terms of the collection of DNA, there are a number of physical sources that are viable, such as blood or saliva. Of the files that contained information on the physical source of the DNA sample (n = 543), in total, there were 770 DNA samples, as more than one physical source of DNA could have been collected per file. As a result, the percentages provided in Figure 2 exceed 100%. The most common source of DNA was from blood (76 percent), followed by saliva (26 percent), and non-fluid DNA (23 percent) (see Figure 2).

Figure 2: physical sources of the DNA samples (n = 543)

Figure 2 illustrates the physical source of the DNA using a bar graph.

Figure 2 - Text equivalent

Figure 2 illustrates the physical source of the DNA using a bar graph. The most common source of DNA was from blood (76 percent), followed by saliva (26 percent), and non-fluid DNA (23 percent). Contact fluid and hair each made up 11%, semen 5% and teeth 1%.

It is interesting to note that there were some variations when comparing the physical source of the DNA sample by the primary nature of the offence. As blood was the most common physical source of DNA overall in this sample, it was not surprising that it was the most common source of DNA for all offence types, with the exception of sexual assault files. Here, semen was the most common physical DNA source. In fact, approximately three-quarters of all the files that used semen as a physical source of DNA (76 percent) were sexual assault cases.Footnote 4 While one might expect that a large proportion of personal offences, such as assaults or robbery, would include blood as a physical source of DNA; blood was also a common physical source of DNA in Break and Enter, and other property crime filesFootnote 5 (see Table 2).

Table 2: physical source of the DNA sample by primary offence type (n = 542)
  Hair Saliva Blood Teeth Bone Semen DNA Non-Fluid Contact Fluid
Homicide (n = 25) 60% 64% 88% 8% 4% 8% 64% 20%
Assault (n = 17) 24% 29% 82% 0 0 0 53% 6%
Sexual Assault (n = 38) 13% 63% 50% 0 0 58% 29% 68%
Robbery (n = 76) 26% 32% 58% 0 0 4% 47% 18%
B & E (n = 333) 2% 17% 83% 0 0 1% 10% 3%
Other Property Crime (n = 5) 0 40% 80% 0 0 0 0 0
Other (n = 48) 21% 27% 58% 0 0 2% 38% 10%

Similar to the multiple sources of physical DNA, such as hair, blood, and saliva, DNA evidence can be collected from a variety of sources. Here, the sources were categorized as from the offender, the victim, and/or the crime scene. Of the 530 files with information on where the DNA sample came from, 657 sources of DNA were included. Overwhelmingly, the source of the DNA sample was from the crime scene (93 percent). The offender was the source of the DNA submission in 15% of files and the victim was the source of DNA in a very similar proportion of files (16 percent). When considering the source of DNA by the nature of the offence, only in cases of sexual assault was the crime scene not the main source of the DNA (see Table 3). For sexual assault files, the most common source of DNA was the victim (82 percent) followed by the offender (26 percent). Unsurprisingly, the victim's DNA was rarely present when the offence was property-related and the offender's DNA was present more often when the offence was violent in nature, such as a homicide or an assault.

Table 3: source of the DNA sample by primary offence type
(n = 527)Footnote 6
  Offender Footnote 7 Crime Scene Victim
Homicide (n = 24) 38% 92% 80%
Assault (n = 13) 54% 85% 46%
Sexual Assault (n = 38) 29% 29% 82%
Robbery (n = 70) 27% 96% 17%
B & E (n = 331) 5% 99% 1%
Other Property Crime (n = 6) 17% 100% 0
Other (n = 45) 31% 98% 33%

Importantly, the time that each step takes in the overall process is critical for assessing the effectiveness of DNA evidence used in an investigation. The files contained several variables associated to time: Request for Approval referred to the date that the request was made of the lab for analysis by the investigator; Approval referred to the date that the request was approved by the lab for analysis; and Forwarded to the Lab referred to the date that the samples were forwarded to the lab to have the analysis completed. Specifically reviewed here is the length of time it took from the date of a Request for Approval to the Forwarded to the Lab date. Again, all these dates were derived from the files themselves. In total, 319 files had the necessary valid information to make the aforementioned calculation. While the maximum amount of time it took was 349 days and the minimum was only one day,Footnote 8 the average amount of time was 43 days. Interestingly, the more "serious" the offence, the faster the DNA samples were received by the lab (see Table 4).Footnote 9

Table 4: mean time in days for DNA samples to be forwarded to the lab for analysis by primary offence type (n = 302)
  Avg. Number of Days
Homicide (n = 3) 2
Assault (n = 7) 17
Sexual Assault (n = 16) 20
Robbery (n = 20) 38
B & E (n = 235) 46
Other Property Crime (n = 3) 154
Other (n = 18) 18

In effect, an analysis of the files indicated that the most common offence in this sample was a Break and Enter, blood was the most common physical source of DNA, the crime scene was the most common source of the DNA, and it took, on average, 43 days from the Request for Approval date to the Forwarded to the Lab date; however, the more serious the offence, the faster the DNA sample was received by the lab.

4. Results from the DNA Lab

Data was available in 117 cases to determine how long it took the lab to provide the results of the DNA analysis.Footnote 10 Again, using the dates provided in the lab analysis outcome reports in the files. On average, in this sample of cases, it took the lab 107 days to confirm results from the date that the lab received the DNA sample with a range of six to 399 days.Footnote 11 As demonstrated in Table 5, while the number of cases was very small for each offence type, which does not allow for the results to be representative, for the most part, there was little variation in the amount of time it took to get results based on the nature of the offence. While the fastest turnaround time in this sample was for sexual assault files (80 days), the offence type with the longest turnaround time was ‘other’ at 126 days.

Table 5: mean time in days for DNA Lab to confirm their results by primary offence type (n = 111)
  Avg. Number of Days
Homicide (n = 0) Footnote 12 -
Assault (n = 3) 114
Sexual Assault (n = 8) 80
Robbery (n = 14) 101
B & E (n = 67) 92
Other Property Crime (n = 3) 100
Other (n = 10) 126

Importantly, the average amount of time for the lab to confirm their results from the date they received the DNA sample for all files in our sample decreased substantially since 2010. Specifically, in 2009, the average length of time it took the lab to respond with results was 117 days (n = 22). While this increased slightly to 122 days in 2010 (n = 36), the length of time dropped substantially in 2011 to just 75 days (n = 35).

In our sample of files, the result of the lab's analysis was recorded in 195 files. In less than two-thirds of the files (61 percent), a DNA profile was developed. In more than one-quarter of files (27 percent), a match was made to a convicted offender, but it was rare (9 percent) that a crime scene to crime scene match was the result of the DNA analysis.

Table 6 presents the breakdown of the lab's results by the nature of the offence. So, for example, with respect to the 16 sexual assault files in our sample, a suspect was identified as a result of the DNA analysis in a slight minority of files (44 percent).Footnote 13 When considering other offence types, a suspect was identified in more than one-third (39 percent) of robbery files and in a similar proportion of ‘other’ offence files (37 percent). Crime scene matches occurred in a few Break and Enter files. Again, when considering these results, it is important to keep in mind that the sample sizes are extremely small.

Table 6: Lab result by primary offence type (n = 193)
  No DNA DNA Profile Developed Convicted Offender Match Crime Scene/Crime Scene Match
Homicide (n = 5) 0 60% 40% 0
Assault (n = 7) 0 86% 14% 0
Sexual Assault (n = 16) 6% 50% 44% 0
Robbery (n = 28) 11% 50% 39% 0
B & E (n = 116) 1% 64% 20% 16%
Other Property Crime (n = 2) 0 100% 0 0
Other (n = 19) 5% 58% 37% 0

In terms of the average amount of time it took the lab to report results based on the outcome of the analysis, as demonstrated in Table 7, it took 110 days for a result of a DNA profile to be produced compared to, on average, 98 days for a result of a convicted offender match to be completed.Footnote 14

Table 7: mean number of day for Lab results
  Mean # of Days
No DNA (n = 2) 137 Days
DNA Profile Developed (n = 37) 110 Days
Convicted Offender Match (n = 17) 98 Days
Crime Scene/Crime Scene Match (n = 10) 61 Days

In considering the mean amount of time it took for the results of the lab to be provided to the investigator based on the outcome of the analysis, as demonstrated in Table 8, there was very little variation. In effect, it took, on average, 111 days for the result of a convicted offender match to be provided to the investigator and 126 days for a DNA profile.Footnote 15 Again, caution is needed in interpreting this data as the sample sizes are very small.

Table 8: mean number of days for Lab results to be provided to the investigator based on the DNA result
  Mean # of Days
No DNA (n = 2) 120 Days
DNA Profile Developed (n = 38) 126 Days
Convicted Offender Match (n = 34) 111 Days
Crime Scene/Crime Scene Match (n = 27) 116 Days

In summary, based on the information in this sample of files, it took the lab approximately 107 days to report the results of the DNA analysis. Most commonly, the analysis resulted in the development of a DNA profile and, to a lesser extent, the identification of a suspect.

5. The Role of DNA in Criminal Investigations and Prosecutions

Given the challenges, cost, and time to properly collect and analyze DNA samples, it is critical that these exhibits contribute to the successful investigation and conviction of offenders. In this sample, 25% of files indicated that the DNA results changed the nature, direction, or scope of the investigation, and nearly two-thirds of the files (63 percent) indicated that the result of the DNA analysis helped identify a suspect.Footnote 16 Of note, when considering specific offence types, DNA was most successful in robbery and Break and Enter files in identifying a suspect, and was also successful in a majority of homicide, assault, sexual assault, and other files (see Table 9). Importantly, in 4% of cases DNA results helped eliminate a suspect.

Table 9: proportion of offence types in which DNA result helped identify a suspect (n = 482)
  % Yes
Homicide (n = 16) 56%
Assault (n = 12) 58%
Sexual Assault (n = 32) 50%
Robbery (n = 61) 62%
B & E (n = 322) 67%
Other Property Crime (n = 4) 25%
Other (n = 34) 53%

In terms of the role of DNA analysis on prosecution, slightly more than one-third of files (36 percent) indicated that DNA helped to lay charges against an offender.Footnote 17 Interestingly, as demonstrated in Table 10, there was some variation by offence type. While the sample sizes were small, DNA helped lay charges in six (55 percent) of our sample's 11 assault cases. DNA also played a role in the laying of charges for almost half of our sample's 32 sexual assault (47 percent) and 57 robbery (47 percent) files. Conversely, in this sample, DNA played no role in the laying of charges for a large majority of Break and Enter files (67 percent), homicide files (79 percent) and ‘other’ offence types (62 percent).

Table 10: proportion of offence types in which DNA helped lay charges (n = 466)
  % Yes
Homicide (n = 14) 21%
Assault (n = 11) 55%
Sexual Assault (n = 32) 47%
Robbery (n = 57) 47%
B & E (n = 316) 33%
Other Property Crime (n = 3) 0
Other (n = 32) 38%

Another important contribution that DNA collection and analysis can play is in linking previously unrelated occurrences. In this sample, a slight minority (42 percent) of files indicated that the DNA analysed provided a link to previously unrelated occurrences. In just over one-third of files (37 percent), the DNA analysis resulted in an application for a DNA warrant. When considering these applications by offence type, a slight majority of assault and ‘other’ offence files (54 percent each) had the DNA result in an application for a DNA warrant (see Table 11). This was less common for sexual assault (47 percent), robbery (39 percent), and Break and Enters (33 percent).

Table 11: proportion of offence types in which DNA resulted in an application for a DNA warrant (n = 484)
  % Yes
Homicide (n = 16) 25%
Assault (n = 13) 54%
Sexual Assault (n = 34) 47%
Robbery (n = 62) 39%
B & E (n = 320) 33%
Other Property Crime (n = 4) 25%
Other (n = 35) 54%

In a slight majority of files (52 percent), a report to Crown Counsel was submitted. The most common reasons for not submitting a report to Crown Counsel were that the investigation and DNA analysis resulted in an inability to identify a suspect or there simply was not enough evidence to proceed. However, in virtually all of the cases (91 percent) where a report to Crown Counsel was submitted, the charges were approved. In those very rare cases (n = 22) where charges were not approved, the main reasons were that too much time had passed since the commission of the offence or a determination that it was unlikely that prosecution would result in a conviction. As demonstrated in Figure 3, the most common offence type in which charges were approved was Break and Enter (49 percent) followed by robbery (20 percent), ‘other’ (13 percent), and sexual assault (11 percent).

Figure 3: distribution of primary offence type when charges were approved (n = 213)

Figure 3 illustrates the distribution of the primary offence type when charges were approved on a bar graph.

Figure 3 - Text equivalent

Figure 3 illustrates the distribution of the primary offence type when charges were approved on a bar graph. The most common offence type in which charges were approved was Break and Enter (49 percent) followed by robbery (20 percent), ‘other’ offence (13 percent), and sexual assault (11 percent). Assault made up 5%, ‘other’ property crimes and homicide made up 1% each.

It should be noted that for all of the homicide, assault, sexual assault, and other property crime the charges were approved. Moreover, in 90% of the robbery, 86% of the Break and Enter, and 90% of the "other" offence files charges were also approved.

While not all cases go to trial, information was available about the court outcome in 155 files. As coded in the police files, nearly two-thirds of the files with the relevant information indicated that the result of the process was that the offender was found guilty (63 percent), in 13% of the files (n = 20) it indicated that the offender plead guilty, and in another 8% of the files (n = 13) the offender plead guilty to a lesser or included offence. In fact, only 2% of files indicated that the offender was found not guilty and only 14% had the charges stayed.

Finally, an analysis was conducted examining what other types of evidence were included for those offences in which charges were approved (see Table 12). Of the 185 files that indicated that additional evidence was provided, 431 additional kinds of evidence were noted, as more than one type of evidence could have been collected. For those offences in which charges were approved, nearly half (48 percent) indicated ‘other’, while a similar proportion of files (47 percent) indicated that at least one photograph was included as evidence, and a slightly smaller proportion of files included fingerprints (44 percent) and clothing (40 percent) as evidence. Very rarely was physical matching (6 percent), a tire impression (1 percent), or a tool mark impression (1 percent) indicated in the files. It should be noted that in a slight minority of files (41 percent), the file indicated that a warned statement was included in the evidence.

Table 12: other types of evidence in those cases in which a charge was approved (n = 185)
  % Yes
Footwear (n = 32) 17%
Clothing (n = 73) 40%
Fingerprints (n = 82) 44%
Video (n = 56) 30%
Photograph (n = 87) 47%
Tire Impression (n = 1) 1%
Tool Mark Impression (n = 1) 1%
Physical Matching (n = 11) 6%
Other' (n = 88) Footnote 18 48%
Warned Statement (n = 76) 41%
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