last one. "Preston '75" was a reference to the murder of Joan Harrison. The Yorkshire Ripper was believed at the time to have killed her, but the supposed connection was wrongly thought not to be in the public domain leading the hoaxer's claim to gain undeserved credibility. Sutcliffe denied any knowledge and was not charged for this crime. It remained unsolved until 2011, when DNA evidence from the crime scene was matched to those of a deceased man named Christopher Smith (died 2008) who had been convicted of other offences, including attempted rape and manslaughter. The "Wearside Jack" tape On 17 June 1979, Humble sent a cassette to Assistant Chief Constable Oldfield, where he introduced himself only under the name "Jack" and claimed responsibility for the Ripper murders to that point. The recording on a cassette tape ended with a segment from the 1978 single "Thank You for Being a Friend" by Andrew Gold. George Oldfield and other senior officers were informed by the FBI that the creator of the tape was a blatant hoaxer. The US profiling expert Robert Ressler indicated, in his co-written book, Whoever Fights Monsters, that he contacted them to inform them immediately after he heard the recording. Despite this, the police focused on Humble's Wearside accent. Together with voice analysts, they decided (based on dialectology) that the accent was distinctive to the Castletown area of Sunderland. This led to 40,000 men being investigated to no avail, as the killer, Sutcliffe, came from Bradford. Police also commenced a substantial publicity campaign, including 'Dial-the-Ripper' hotlines, 5,000 billboards, and advertisements in 300 newspapers. Around £1 million was invested in the publicity campaign alone. A few weeks after being played the recording, the voice experts began to try to persuade the police that the tape was created by a hoaxer, but were not listened to. Interviewed by Joan Smith for The Sunday Times in 1980, Olive Smelt, a victim of Sutcliffe who survived his 1975 attack in Halifax, was angry that the police had ignored her insistence that the perpetrator was a local man. Other survivors' evidence, photofits which were close to Sutcliffe's appearance, were also rejected. A confidential police document issued in September 1979 by the West Yorkshire Police murder incident room instructed detectives to disregard from their inquiries any suspect without a North-East accent. Peter Sutcliffe, who committed the murders, was interviewed and released nine times over