I believe that DNA profiling can determine identity, as one's DNA is unique, at least, they say, 33million-to-one certainty. The problems arise when the sample hasn't been properly collected, is contaminated or insufficient in quantity to analyse with any degree of success. Also, the presence of someone's DNA doesn't exclude he possibility of other individuals having being present, thus one cannot necessarily say the DNA's owner was the actual perpetrator of the crime, merely that at some point, they were there.

"abysmal ignorance..." Greg?? Don't understand why a straightforward question should provoke that response! Rather arrogant of you, IMO.