The officers planted heroin on an inmate at Kilmarnock Prison

David Allen, 44, of East Kilbride, a former supervisor at Kilmarnock Prison, was jailed for two years for attempting to pervert the course of justice.

He was sentenced alongside John Robertson, 26, of Auchinleck, Ayrshire, who received 300 hours' community service for helping to plant the drugs.

The two warders were sentenced at the High Court in Edinburgh on Tuesday.

Cell search

During the duo's trial in Kilmarnock last month, the High Court heard how Allen took the class A drug from one prisoner before putting it in the possession of another.

A unit supervisor, he ordered Robertson to place the illegal substance into 22-year-old inmate Steven Little's belongings after he had searched his cell in 2002.

Ex-prisoner Mr Little, 22, of Mossblown, Ayrshire, had been allowed to keep painkillers in his cell due to a toothache and migraine.

But when the capsules were seized by Robertson during a cell search, the probationary warder was ordered to plant a blue wrap of heroin in with them by Allen.

'Stitch-up'

The court heard how Robertson, who had been in his job for only a short period, initially refused to do so but capitulated under pressure from his boss for fear of losing his job.

He eventually owned up to his crime but by the time he had confessed to his superiors other staff had already reported the duo's actions to the prison's management.

The court also heard evidence from two other prison staff who said this had been part of a plan by Allen to "stitch up" Mr Little.

We are grateful to those staff, whose actions have supported this outcome and ensured that illegal activity is not tolerated within Kilmarnock Premier Prison Services

The victim of the plant had been serving an eight-month sentence at the time. He was accused of possession of heroin and could have been prosecuted.

Sentencing Allen, Judge Lord MacFadzean said: "The offence is a very serious matter from someone who was a relatively senior officer at the prison.

"The jury's verdict identified you as the prime motivator in the scheme.

"You were the senior of the two officers involved.

"There is only one appropriate punishment and that is a custodial sentence."

The judge told Robertson: "The evidence shows you were not the instigator. You were drawn into it by a senior officer, who could also influence your own future in the prison service.

"In your case I feel I can avoid imposing a custodial sentence. But for this lapse you have led a law-abiding life."

'Bad decisions'

Kilmarnock Prison is run by private firm Premier Prison Services Limited which has a 25-year contract.

A spokesman for company confirmed both Allen and Robertson no longer worked for the company.

In a statement, it said: "While pleased that the legal system has been able to take its course and mete out punishment for the illegal activities carried out by these two men, it is disappointing to see people make bad decisions that lead to such a negative outcome for them and the people around them.