A prolific mugger who carried out dozens of robberies in Liverpool was sentenced to three years detention today.

Liverpool Crown Court heard that John Keenan's victims included a 15-year-old boy on his way to a cadet's meeting, and he like the others, was threatened that he would be stabbed.

19-year-old Keenan, who was accompanied by others each time, also robbed two students who were playing frisbee near their accommodation in the Lime Street area.

Keenan, of Whetstone Lane, Birkenhead, pleaded guilty to four robberies, which all took place in April and had 51 other offences, including 32 robberies, taken into consideration.

Sentencing him Judge Gerald Clifton said, "These offences involved muggings, you and others terrified wholly innocent members of the public into handing over their valuables by intimidating and threatening them with stabbing and other bullying means."

He said that he had punched one victim, though no injury was caused, and though knife threats were made no knife was used or recovered.

Thomas Keaney, defending, said that Keenan had been using cocaine since 2006 which led him into dishonesty and custodial sentences. He was young and vulnerable and others had taken advantage of him.

Keenan had described this crime spree as "several months of madness" and blames cocaine. He has now matured and wants to obtain qualifications and go on to help other youngsters stay out of trouble, he said.