Yoscow--a deliberate murder, planned in advance by several of a gang, to get rid of a young bully who had made himself generally unpleasant.

There was Childs, who had killed, as he claimed, in self-defence because he was set upon and assaulted by rival runners from another seaman's boarding house.

Really it began to look as if men killed for a lot of reasons.
One consideration at once suggested itself.

How about the killings where the murderer is never caught?
The prisoners tried for murder are only a mere fraction of those who commit murder.

True, and the more deliberate the murder, the greater, unfortunately, the chance of the villain getting away.