- Course Introduction
- 01: Evidence & DNA
- 02: Forensic Biology
- 03: DNA Extraction & Quantitation
- 04: DNA Amplification
- 05: Amplified DNA Product Separation
- 06: STR Data Analysis & Interpretation
- 07: Population Genetics & Statistics
- 08: Communicating Results
- 09: Other DNA Markers & Technologies
- Course Resources
- Laboratory Training Manual
President's DNA Initiative
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Advancing Justice Through DNA Technology
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Advancing Justice Through DNA Technology
DNA Analyst Training
Interpretation Guidelines
Home > Other DNA Markers & Technologies > Other Nuclear DNA Markers and Technologies > Low Copy Number DNA > Interpretation Guidelines
LCN DNA analysis requires the development and implementation of special interpretation guidelines. While these may differ in detail between laboratories, a number of general principles can be enumerated:17
- Every allele in the evidence sample that is reported should be replicated by duplicate analysis
- Heterozygous peak ratios are not a robust measure of allelic association
- Negative controls that contain alleles consistent with the evidence profile require that the evidence samples be re-analyzed. Negative controls with alleles present that do not correspond with alleles in the evidence samples may be ignored, with caution.
- Allele drop out in the evidence sample has to be considered a possibility at those loci exhibiting an apparent homozygous profile.
- If there is a single allele in the evidence profile that does not match the potential donor’s profile then allelic drop-in should be considered.
LCN Case Example |
Fourteen-year-old Marion Crofts was last seen cycling from her home in Fleet, Hampshire, England, to band practice when she was attacked as she passed some bushes close to a canal towpath in Aldershot in 1981. She had been raped, beaten and strangled. Despite a major investigation by Hampshire Constabulary who looked at 24,000 potential suspects, Marion's killer was never found.
A laboratory microscope slide - containing samples collected by the Forensic Science Service (FSS) from the teenager's body after her murder - lay deliberately untouched for 20 years. Scientists knew that they risked losing the evidence for good unless they waited until DNA profiling techniques became more advanced. In 1999, the Forensic Science Service (FSS) developed the super-sensitive DNA Low Copy Number (DNA LCN) technology. Using this technique, they were able to find a full DNA profile of Marion’s suspected killer from some of her clothing. This profile was then loaded onto the UK’s National DNA Database®. In August 2001, a match was found when Tony Jasinskyj was arrested for another crime and his DNA sample was routinely loaded onto the Database. Scientists then returned to the archived laboratory microscope slide to see if they could obtain a DNA profile from the 20-year-old sample that might match the suspect's and further strengthen the case against him. A full profile was obtained that matched with the one from Marion's clothing and the suspect himself, providing strong evidence for the police.
At the time of the murder Jasinskyj was a cook at the local army barracks and he, like 1,500 other soldiers, had been asked to fill out a questionnaire about Marion's death. On it he denied ever having been near the place where she was killed and claimed he was at work at the time. When he was questioned about how his bodily fluids ended up at the crime scene, he said they had been planted there. Tony Jasinskyj was found guilty of the teenager's rape and murder and jailed for life in May 2002. |
http://www.forensic.gov.uk/forensic_t/index.htm © Crown Copyright 2005 |
