David Frediani

David Frediani - AP Photo
In 2000, David Frediani was convicted of the murder of Helena Greenwood. A key piece of evidence: Frediani's DNA was found in skin particles underneath Greenwood's fingernails. Ironically, at the time of her death in 1984, Greenwood, a biochemist, was working to find new uses for DNA technology. She was strangled to death in her San Diego home in 1985. Authorities had suspected Frediani of the crime, but had not had enough evidence to convict him.