Lösel’s extensive analyses of treatment and rehabilitation programmes for offenders have been instrumental in identifying the factors that make programmes successful.

Field experiments in a German prison and global systematic reviews

Lösel’s early work includes a randomised field experiment in a German prison, where he demonstrated the effectiveness of a training programme for prison staff in treating prisoners with greater human dignity. His later work demonstrated the fallacy of the ‘nothing works’ view of rehabilitation programmes for convicted criminals. In a series of systematic analyses of hundreds of independent studies, he found clear evidence of the effectiveness of a range of rehabilitation programmes for various types of offenders, including sex offenders. The overall conclusion of his work is that recidivism can be reduced by providing rehabilitation programmes for convicted criminals, rather than merely imprisonment.

Lösel’s systematic testing of a wide range of crime prevention strategies, included programmes for young children and their families and programmes for rehabilitating convicted criminals. His research has focused on the causes and treatment of juvenile crimes, football hooliganism, school bullying and adult sexual offences. As a pioneer in systematic reviews of all available evaluations of a given programme, he has shown that investing in children’s skills training at an early age can prevent a large amount of crime, saving significant costs of incarcerating adults. He has also shown that the effectiveness of a wide range of rehabilitative treatments for adult sex offenders in reducing recidivism, may depend on the degree of consistency in implementation.

New knowledge within criminology

By carefully testing key crime measures and theories, Lösel has helped to develop the concept of ‘resilience’: the protective factors that help prevent young people from becoming criminals despite being exposed to risk factors such as living in high-crime areas.