many of whom were prosecuted, but whose cases later collapsed. He was prosecuted himself for a small number of offences, admitting to nearly 70, and sentenced to six years in jail, the light sentence being part of the deal for giving evidence against others. He later wrote to the solicitors of those he had implicated to explain that his evidence was made under duress. Once convicted, he refused to make any further statements for the police. Violence, intimidation and torture Allegations were made in the early 1980s that SCS officers placed plastic bags over the heads of suspects, and covered their mouths, in order to partially suffocate them and extract a confession. Kaye notes that no allegation occurred after 1983. In Keith Twitchell's 1980 case, he underwent a polygraph test and a 'truth drug' test to try to establish that this had happened, but the evidence was deemed inadmissible by the court at the time. In 1982–3, some of the accused in the Operation Cat convictions made the same allegation. In Derek Treadaway's case, a Home Office pathologist gave evidence that abrasions around his mouth and bruising on his shoulders and chest were consistent with his account of being held down on a chair and "plastic bagged" with his mouth covered. Allegations of violence also declined, with many fewer after 1986, according to Kaye. Explanations for the decline in violence may include that it proved counter-productive, as evidence of physical abuse could be recorded and presented in court and that psychological pressure in obtaining confessions could be just as effective. However, there were many serious allegations of violence towards suspects in the SCS's earlier history, the best known of which is that of the Birmingham Six. Derek Boswell made well-documented allegations in 1983, after he refused to make a statement. He claimed that an unknown officer entered his cell, beat him up and told him to make a statement. He was later visited by a doctor who recorded that he had blood stains on his T-shirt and trousers, blood clots in his nostrils and minor facial injuries, consistent with his account of being hit in the face. The officer was never identified, although Boswell gave a description of him at the time. One SCS officer was convicted in 1983 of beating up suspects on the evidence of a police cadet, who was subsequently ostracised and resigned. As violence declined, complaints