POLICE in West Devon are working with Dartmoor Prison to clamp down on mobile phone usage in the jail, after fears that they are being used to intimidate witnesses and victims.

A total of 48 phones and 36 SIM cards were confiscated at the Category B prison over the past 12 months.

Traditionally convicts caught using mobile phones suffered sanctions enforced by the prison governor, such as loss of privileges or days added to their sentence. However, the recent crackdown, which was launched on July 1 this year, has so far seen three men appear at Plymouth Magistrates' Court.

Convicted drug dealer Jason Crocker was sentenced to 16 weeks to be served concurrently — not in addition — to his existing jail sentence of five years and four months in December 2013 for conspiracy to supply heroin. The charge of having a prohibited item in prison without authority can result in up to two years extra added to a convict's sentence.

The court heard how interrogation of Crocker's Blackberry mobile showed it had been used to take photographs and video inside the prison while he had claimed he had only used it to contact friends and family.

Detective Constable Wayne Thielmann of Tavistock police said around a dozen cases had been investigated. He said police believed Crocker was using the phone to access social media but as Blackberry Messenger (BBN) was untraceable they were not sure who he had contacted.

'Mobile phones are a source of intimidation both inside and outside the prison,' he said. 'We know that nationally there are cases where prisoners have used mobile phones to threaten and intimidate witnesses and victims, while some will used them to keep in contact with their criminal colleagues as well as their friends and family members.'

He said the police also knew that mobile phones had been used to make arrangements for delivery of illicit substances.

In 2011 and 2012 several people were questioned and some arrests were made after mobile phones wrapped in cling film and drugs were seized near the prison believed to be destined for the jail.

Det Con Thielmann said it was a nationwide problem recognised by the Government and not just specific to HMP Dartmoor.

He said police would be carrying out additional patrols around the prison perimeter to prevent the delivery of mobile phones by the convicts' associates.

A spokesman for the Ministry of Justice's National Offender Management Service said these recent convictions should leave no prisoner in any doubt that if they broke the rules they would face tough punishments.