Intended Learning Outcomes
On completion of this module the student will be able to:
1. Evaluate the principles, practices and applications of forensic DNA analysis techniques (coursework)
2. Critically evaluate scientific findings in the context of a case study (coursework)
3. Demonstrate an understanding of techniques applicable to current forensic DNA analysis ?methods (coursework)
Scenario
On 14thFebruary 2016 at approximately 08:30 the body of a female was discovered slumped in some bushes in Stanley Park, North Shields. A suspected semen stain was located on the victim's inner thigh. An indirect acid phosphatase test gave a positive reaction and the stain was collected on to a DNA-free cotton swab head for further analysis. This sample was labelled as BS/05. No other external stains were observed during the initial examination.
At the laboratory cell harvesting was carried out for all submitted swabs and 1μl was used to prepare microscope slides to search for spermatozoa. Using a high power microscope set at 400x many spermatozoa were observed in every field of view for the sample collected from the inner thigh of the victim and the sample was sent for DNA analysis. A full male DNA profile was obtained using the NGM SElect PCR amplification kit.
Police enquiries have identified the victim as Mrs. Jessica Stones (DOB: 14/08/84) and identified Mr William Doyle (DOB: 28/03/78) as a suspect. Mr Doyle was arrested on 16thFebruary 2016 and a DNA sample in the form of a buccal swab was collected (LB/01). This swab was submitted to the laboratory on 16thFebruary 2016 and a full NGM Select DNA profile was obtained. Mr Doyle denies any involvement with this crime.
NGM SElect PCR amplification kit results for BS/05 and LB/01 relating to the semen stain collected from Mrs.Stones thigh and the buccal swab collected from Mr Doyle are shown in the table below.
| LOCI |
STAIN (BS/05) |
DOYLE (LB/01) |
| D3S1358 |
15, 16 |
17, 17 |
| vWA |
14, 16 |
17, 18 |
| D16S539 |
9, 10 |
8, 12 |
| D2S1338 |
20, 23 |
19, 22 |
| Amel |
X, Y |
X, Y |
| D8S1179 |
12, 13 |
14, 16 |
| D21S11 |
28, 31 |
28, 30 |
| D18S51 |
12, 15 |
17, 19 |
| D19S433 |
14, 15 |
13, 14.2 |
| THO1 |
7, 9.3 |
7, 7 |
| FGA |
24, 26 |
19, 20 |
| D10S1248 |
12, 15 |
12, 14 |
| D22S1045 |
11, 16 |
14, 15 |
| D2S441 |
14, 15 |
10, 13 |
| D1S1656 |
13, 16 |
15, 15 |
| D12S391 |
18, 19 |
17, 18 |
| SE33 |
17, 25.2 |
20, 23.2 |
Question 1
Acting as a forensic DNA analyst, prepare a short summary to explain the science of forensic STR profiling for the Police Officers (non-experts) investigating this case.
Your answer should (briefly) consider
1. What DNA is?
2. Why it can be used?
3. Why STR markers are examined?
4. What you would expect to see in the case of a match and a non-match between crime scene and suspect reference profiles.
Question 2
Following comparison of Mr Doyle's DNA profile to that relating to the crime scene stain he can be excluded as a potential source of the semen on Mrs Stone's inner thigh.
Describe
• How the National DNA Database can be used to provide the Police with new investigative leads.
Your answer should include
1. An explanation of the what the National DNA Database is
2. What data is added to it i.e. STR profile results and may include comment on success rates for speculative searches on the UK National DNA Database.
The information provided in your report should be qualified by reference to source materials (i.e. journal articles) in the Harvard style.