News that the FBI crime laboratory found no semen on the dress means there will be no need for DNA analysis that might have suggested that President Clinton had a sexual enounter with Lewinsky.
The Bureau received the now-famous Navy blue cocktail dress from special prosecutor Ken Starr on July 29 and began testing it on July 31.
The Bureau declined to disclose any information about the tests, but DNA experts outlined standard procedures that the lab would have followed to determine the existence of semen.
FBI technicians would have first subjected the stain on Lewinsky's dress to a pair of chemical tests. The first test would have revealed the presence of an enzyme found in high concentrations in seminal fluid. The second test would have detected a protein called "P-30" that is found in seminal fluid.
"The two together are essentially unique to human semen," said Prof. Walter Rowe of George Washington University, a forensic scientist and an expert on DNA.
The FBI may also have slipped a sample from the stain under a powerful microscope to look for sperm.
Rowe and other DNA experts interviewed by CBS.com said it should have taken the Bureau no more than 24 hours to determine the presence or absence of sperm on the dress.
If that's the case, Starr has known for some time that the dress was a dead end.
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