The crimes were initially believed to have been committed by a mentally challenged 17-year-old by the name of Richard Buckland, who under questioning admitted the murder of Dawn Ashworth. That is until Alec Jeffries, who along with Peter Gill and Dave Werrett, developed the science of DNA fingerprinting - and with the cooperation of Leicestershire Constabulary - mass screened 5,500 men over a six month period. The perpetrator was not identified, because the guilty man had commandeered one of his work colleagues to stand in for him.
Ian Kelly admitted to fellow workers in a pub that he had given blood under the assumed identity of his colleague and was subsequently reported to police by a woman who overheard his admission. This ultimately led to the arrest of bakery worker, Colin Pitchfork on September 19th 1987, whose DNA fingerprint matched the semen samples recovered from both girls. It also exonerated Richard Buckland. Colin Pitchfork was sentenced to a minimum term of 30 years, later reduced to 28.
Ironically, the murder of Dawn Ashworth would come on the seventeen year anniversary of the trinity of Zodiac letters mailed to the San Francisco Chronicle, San Francisco Examiner and Vallejo Times-Herald on July 31st 1969 - and the subject of DNA speculation to this day. The Zodiac letters have undergone much scrutiny with regards to securing DNA from behind the envelope seals and stamps. But to this day, the case appears as cold as the night when David Faraday and Betty Lou Jensen were callously murdered in Benicia, California on December 20th 1968. There has been a raging debate on whether any Zodiac DNA exists on the letters from 1969 and 1970, either because of degradation, mishandling and bad storage. Or whether the Zodiac Killer ever licked the stamps and envelopes at all. This argument could be put to bed once and for all, by testing the 1986 and 1987 Zodiac letters. Incorrectly labelled as hoaxed letters, both communications can be linked by one author, as well as to the 1969 Vallejo Times-Herald envelope, which we know was mailed by the genuine Zodiac Killer.
Testing both letters would finally answer the crucial question to the satisfaction of everybody, of whether  The 1986 and 1987 letters were licked by the same author and sender, and  Whether either letters were licked at all. These communications should have been stored correctly (despite being deemed inauthentic by handwriting experts) - and if so - should be the first port of call in the search for DNA from the Zodiac Killer. But they won't be.