Reporting DNA results

What is a basic explanation of DNA?

Genetic material found in cells throughout our bodies - a person’s DAN is the same no matter which tissue or bodily fluid it originates

Give an overview of DNA analysis

Several different areas of DNA analyzed, each of which will differ from person to person. A person will have 2 types of DNA at each area, one inherited from each parent. 21 areas are analyzed, known as short tandem repeats.

Explain amplification of DNA

DNA can be extracted from very small samples, and 11 areas of DNA to be analyzed can be copied or ‘amplified’. This process is referred to as polymerase chain reaction PCR. During this process, many copies of 24 DNA areas of interest are made, resulting in sufficient DNA to analyze.

Explain how DNA profile is produced?

After DNA amplification, samples are run in an instrument to separate different areas and with computer-aided analysis, a profile consisting of up to 48 DNA types can be seen. DNA profiles obtained from crime scene stains can then be compared with DNA profiles obtained from reference samples.

Explain the terms ‘match or exclusion’?

If a persons DNA differs from that of crime scene samples then he or she can be excluded as a contributor of that sample - however if same DNA profile is obtained from crime and reference sample then this is described as a match.

Explain how a match is evaluated?

If someone else is unrelated to that person who is the contributor of the crime sample DNA, the probability of finding such matching DNA profiles can be calculated.

What are the 4 result types that may be observed?

Full profile, partial profile, mixed profile, unsuccessful

What should you say when reporting a DNA match?

The estimated probability of finding such matching DNA profiles, if another male unrelated to Mr B is the contributor of the DNA, is more than 1 billion.

What should you say when reporting a DNA exclusion?

Stain 1 gave a complete DNA profile which did not match any of the comparison samples analyzed in this case