Britain mandated the diminished responsibility defense in 1957 as a means of circumventing the difficulties of the mandatory murder sentence, which at that time was death for some classes of murder and life imprisonment for others. The death penalty has been abolished, but the diminished responsibility defense remains as a device for circumventing the mandatory life sentence for murder. This study focuses on a change in recent years on the sentences given those who have successfully used this defense. In 1964, half of the diminished-responsibility offenders were given hospital orders, with an increase to 70 percent by the end of the decade. The proportion of hospital orders then started to decline, falling to a third in the 1970's and then to one-fourth; simultaneously, the use of imprisonment for these offenders increased substantially. This research, begun in 1978, focused on the years 1966-77. A two-thirds sample was randomly selected from the diminished capacity offenders for 1966-69 and a one-third sample from the offenders convicted in 1970-77, yielding a total sample of 253 men. The basic data source was the prosecution's documentation for each case. Findings show that the underlying reason for the sentencing change was the reduction in the number of cases for which reporting doctors recommended a hospital order. The judges then sentenced most offenders to custodial rather than noncustodial sentences apparently for the purpose of retribution. The confusion in sentencing such offenders would be reduced if both the mandatory sentence for murder and the diminished responsibility defense were abolished, thus enabling judges to sentence in murder cases based upon particular mitigating and aggravating factors. Tabular and graphic data, a subject index, and 35 reference listings are provided.