Herbert Leonard Mills killed Mrs Mabel Tattershaw simply to see if he could commit the perfect murder. After the event he then tried to sell his story to the police so financial gain was also evident.

When a twelve year old boy commits a murder it is always difficult to work out exactly why. Ciaran Collins had at the time been in council care but had no history of violence. When the police searched his room amongst his belongings was a book entitled 'One was not enough' which was about multiple murders so perhaps he simply wanted to know what it would be like

When Harold Jones confessed to murdering 8 year old Freda Burnell and 11 year old Florence Irene Little he said the reason was a desire to kill. Both of his victims had been sexually molested as well

Nathan Leopold and Richard Loeb murdered Bobby Franks because they wanted to commit a perfect murder which they thought would be impossible to detect.