Forensic evidence, it turned out, was scant. Although testing showed the presence of male human DNA from the woman, there was no way to match it to Mr. Roethlisberger or anyone else, according to Ted R. Staples, GBI's manager of forensic biology.
"It was an extremely small quantity of that, and there simply was not enough to generate a nuclear DNA profile from that male" Mr. Staples said. "We carried it forward and made an attempt [to obtain a DNA profile.] The only profile generated was that of the female."
Even with today's technology, the sample was so infinitesimal that nothing could be determined.
"Normally what we're looking for is about a nanogram of DNA, which is a billionth of a gram. A raisin weighs about a gram, so if you could cut a raisin into a billion pieces, we need one of those. So this particular result was far less than even a nanogram. There was something there. It just wasn't enough."
Mr. Staples said scientists could not discern the source of the DNA in the sample, whether it was from saliva, semen or something else.
Read more: http://www.post-gazette.com/pg/10108/10 ... z0lZ83Gpwk