Quote Originally Posted by Rajagra View Post
Excuse me, but how in hell can DNA evidence prove someone is innocent? All it can do is prove some kind of connection between a person and a place.

It cannot prove a person was not in a given place.
It cannot prove a person did not do something.

You are right that witnesses are unreliable. But so is faulty logic applied to DNA results.

Personally I have grave doubts about the reliability of DNA evidence. There is an assumption that all the "bands" shown in the result are independent, and that you can apply probability formulae as such. What if those bands aren't independent? We are all human after all, and DNA patterns are a blueprint, they have to follow some basic pattern in order to create a human being. All those one in 50 million probabilities they throw out to support their reliability would be completely bogus. I've never seen proof that DNA evidence is as reliable as they claim, yet we are all supposed to accept that it is infallible.

Also DNA testing has become incredibly sensitive. The tiniest amount of material can be tested. We are already past the point where a dead skin cell or hair can fall off, be blown across a city and land at a crime scene, then be used to "prove" a connection. Sooner or later someone will be found guilty of a crime because of this assumption that DNA evidence is infallible, maybe it has happened already.

Sorry, I guess.
Easy. DNA evidence is routinely used to rule out the possibility of the accused being the perpetrator. Example: woman gets raped and murdered. Someone identifies the accused as the perpetrator. Based on the witness ID (and possibly other circumstantial evidence) the accused is convicted and sentenced. DNA testing wasn't available at the time. Sperm and blood samples taken from the victim are now subject to DNA testing, and show no match to the convicted guy. In other words-the sperm and blood didn't come from the guy sitting on death row. This scenario has played out far too many times. Google "Project Innocence" for a host of examples. The DNA acts to exonerate the accused who was accused based on forensic evidence that can now be shown not to have come from the accused. As far as your point about the alleged unreliability of DNA testing--this issue has already been argued in the courts and I'm not aware of any jurisdiction that does not recognize the scientific reliability and dependability of DNA testing. Ir's far, far more accurate than the old blood sample testing that the courts relied upon for decades.