A match made between a crime scene profile and an individual profile identifies a possible suspect. A match made between different crime scene profiles indicates a repeat offender at work.
The police may use this DNA evidence to help prosecute someone for a crime.
Complete DNA profiles give very reliable matches and provide strong evidence that the suspect is guilty. Match results are more open to interpretation if the original sample contained more than one person's DNA or yielded only a partial profile*.
Anyone considering DNA evidence in a trial should be aware of any potential issues.
*Partial profile: an incomplete DNA profile obtained because the original sample contained only a tiny amount of DNA or the DNA was degraded. Often derived from crime scene samples.
The statistical information used alongside DNA evidence in court can be confusing for non-scientists. For example, saying that a profile could occur in one in a million people in the UK does not mean that the chance of the defendant being innocent is one in a million.
