John Straffen returned home to Bath in March 1946, where the Medical Officer of Health examined him and found he still warranted certification under the Mental Deficiency Act. After several short-term jobs, he found a place as a machinist in a clothing factory. Early in 1947, Straffen began to go into unoccupied homes and steal small items to hide them; he never brought them home or gave the items to others. Straffen had no friends and began stealing without being enticed by others. On 27 July 1947, a 13-year-old girl reported to police that a boy called John had assaulted her by putting his hand over her mouth and saying: “What would you do if I killed you? I have done it before.” This incident was not connected to Straffen until later. Six weeks later, Straffen was found to have strangled five chickens belonging to the father of a girl with whom he had quarrelled. When arrested, Straffen was also under suspicion for burglary and in interview cheerfully confessed to it and many other incidents to which he had not been connected. He was remanded in custody, and the Medical Officer of Horfield prison examined him, certifying that he was mentally retarded. On 10 October, Straffen was committed to Hortham Colony in Bristol under the Mental Deficiency Act 1913. Hortham was an “open” colony which specialised in training mentally disabled offenders for resettlement in the community. As he had been under investigation for burglary, Straffen’s certificate stated that he was “not of violent or dangerous propensities.” He was well-behaved at Hortham and kept away from other inmates. As a result, in July 1949, he was transferred to a lower-security agricultural hostel in Winchester. There he did well initially, but fell back into old ways when he stole a bag of walnuts and was sent back to Hortham in February 1950. In August 1950, Straffen got in trouble with Hortham authorities when he went home without leave and resisted the police when they went to recapture him.

In 1951, John Straffen was examined at a Bristol hospital, where electroencephalograph readings showed that he had suffered “wide and severe damage to the cerebral cortex, probably from an attack of encephalitis in India before the age of six.” By now, however, Straffen was considered sufficiently rehabilitated to be allowed a period of unescorted home leave. He used the time to get a job at a market garden, which he was allowed to keep. Hortham licensed him to the care of his mother, as the family home was less overcrowded. When Straffen’s 21st birthday came, under the Mental Deficiency Act, he had to be reassessed by Hortham, which continued his certificate for a further five years; the family disputed the assessment and appealed. As a result, the Medical Officer of Health for Bath examined Straffen again on 10 July 1951 and found improvement in mental age to 10; he recommended that Straffen’s certificate be renewed only for six months with a view to discharge at the end. According to Letitia Fairfield in the introduction to the “Notable British Trials” series volume about Straffen, Straffen had a “smouldering hatred” and an “intense resentment” of the police and blamed them for all his troubles from the age of eight. On the morning of Straffen’s assessment, a young girl named Christine Butcher was murdered. Fairfield speculates that Straffen saw the press coverage that followed and made the connection that strangling young girls gave the maximum amount of trouble to the police.

On 15 July 1951, John Straffen went to the cinema, on his own. His route took him past 1 Camden Crescent in Bath, where 5-year-old Brenda Goddard lived with her foster parents. According to Straffen’s later statement to the police, he saw Brenda gathering flowers and offered to show her a better place. He lifted Brenda over a fence into a copse, after which she fell and hit her head on a stone. She was unconscious, and he strangled her. Straffen did not make any attempt to hide the body and simply went on to the cinema (to see the film Shockproof) and returned home. Although Bath police had not previously suspected Straffen was violent, he was considered a suspect in the murder and seen by police on 3 August. Meanwhile, the police had visited Straffen’s employer to check on his movements; this resulted in Straffen being dismissed on 31 July. In a later interview with a prison psychiatrist, Straffen said that he knew he was under suspicion and wanted to annoy the police, because he hated them for shadowing him. On 8 August, John Straffen was again at the cinema when he met 9-year-old Cicely Batstone. He first took Cicely to a different cinema to see another film and then went on the bus to a meadow known as “Tumps” on the outskirts of Bath. There he strangled her to death. The circumstances of the murder left many witnesses who had seen Straffen with the girl. The bus conductor recognised Straffen as a former workmate, a courting couple in the meadow had seen Straffen very closely, and a policeman’s wife had also seen the two together. She mentioned it to her husband; when the alarm was raised the next morning, she guided police to where she had seen the two, and the body of Cicely Batstone was discovered. Her description of the man was enough to identify Straffen immediately as the suspect.

Accordingly, the police drove to John Straffen’s home and arrested him for the murder of Cicely Batstone on the morning of 9 August. Straffen made a statement admitting he had killed Cicely Batstone and also confessed to the murder of Brenda Goddard: “The other girl, I did her the same.” He was duly charged with murder and remanded in custody. On 31 August, after a two-day hearing at Bath Magistrates’ Court, Straffen was committed for trial for the murder of Brenda Goddard. At Taunton Assize Court, on 17 October 1951, Straffen stood trial for murder before Mr Justice Oliver. However, the only witness to be heard was Dr. Peter Parkes, medical officer at Horfield Prison, who testified to Straffen’s medical history and stated his conclusion that Straffen was unfit to plead. Oliver commented: “In this country we do not try people who are insane. You might as well try a baby in arms. If a man cannot understand what is going on, he cannot be tried.” The jury formally returned a verdict that Straffen was insane and unfit to plead. John Straffen was removed to Broadmoor Institution in Berkshire. Broadmoor had originally been termed a criminal lunatic asylum, but by the Criminal Justice Act 1948, responsibility for it had been transferred to the Ministry of Health, and those committed to it had been renamed patients. Inside Broadmoor, Straffen was given a job as a cleaner.

John Straffen died at Frankland Prison in County Durham on 19 November 2007 at the age of 77. He had been in prison for a British record of 55 years. Moors Murderer Ian Brady (who had been in prison since October 1965 and was then in Ashworth Hospital) became Britain’s longest-serving prisoner.