This article was most interesting, given much of the fora discussions going on right now. It is easy to understand and should end many of the invalid arguments currently underway.

http://www.ugc.edu.hk/rgc/rgcnews7/Pages/DNA-E.html

Key Points:

Statisticians at The University of Hong Kong have been helping to solve crime scene complications where potential evidence is stained with DNA from more than one person.

For a positive identification, forensic investigations involving DNA often need at least nine matches at sites, or loci, identified at specific points across the 23 pairs of chromosomes found in humans.

All loci are “non-coding” which means they do not describe the colour of skin, hair, eyes, or ethnic orientation.

“We wanted to find out which sites were the least related. The more unrelated the sites are, the easier the calculation.” With mixed DNA stains from a crime scene, samples found by forensic detectives may include DNA from both the victim and perpetrator.

“In mixed stains, we can identify the DNA fragments contributed by the victim which leaves the remaining DNA fragments for comparison with the suspect.”
Comment: The statistical results from a DNA "match" is what is important. This indicates that the specific loci found to match (between forensic DNA and a suspect's DNA) alters the calculation.

The theorems he obtained can be used in cases where more than 10 people are involved, as well as for multi-ethnic groups and relatives of suspects where DNA similarities may exist.