Four men have been convicted of vandalising a field containing GM crops in Midlothian.

Mark Ballard, Matthew Herbert, James Mackenzie and Alan Tolmie had denied deliberately destroying the oilseed rape plants being grown at Boghall Farm near Dalkeith in March 1999.

They argued that what they did was reasonable, given what they alleged were the potentially grave dangers to the environment.

However, the four were found guilty at Edinburgh Sheriff Court on Monday morning.

Ballard, Herbert and MacKenzie were each fined £125, while Tolmie was fined £250.

But the four later pledged that their campaign would continue - and said they were considering an appeal.

Ballard - a Green Party spokesman and chairman of the advisory board for the youth wing of Friends of the Earth Europe - said: "We took the step in the knowledge of what might happen, but in the certainty that we had to stop this.

"I am sure that history will vindicate us. We will be proven right in the end when people see the problems."

Mackenzie said: "We are surprised that the sheriff has decided to find us guilty as we felt there was enough evidence to show that our actions were reasonable.

Environmental protesters

"But you can be reassured that the campaign against the testing of GM crops will continue, despite this verdict."

Green Party MSP Robin Harper said: "We are disappointed at the verdict and, although the Scottish Green Party doesn't condemn or condone direct action, it doesn't mean we don't have a great deal of sympathy for those people who may take this kind of action.

"I don't think that this verdict is a setback and I think people will continue to protest in this way as there is a great depth of feeling in many parts of Scotland against these field trials."

Ballard, 29, a graphic designer from Stockbridge, Edinburgh; Herbert, 28, a researcher from St Andrews; Tolmie, 33, a professional busker from Edinburgh and Mackenzie, 28, a press officer from Stockbridge, had earlier been found not guilty of obstructing police during the demonstration.

Six other environmental protesters were also cleared of the same charge last May.

During the trial Sheriff Elizabeth Jarvie, QC, heard that 100 demonstrators had gathered at the Midlothian farm.

A group of activists jumped over the fence into a field where a GM crop trial was growing and some started pulling up oilseed rape plants.

But the trial plants were hidden within a larger commercial crop - and the activists attacked an unmodified, decoy area leaving the test area untouched.

They caused only £1.50 worth of damage.

The plant trial, co-ordinated by the UK Government and carried out by the Scottish Agricultural College (SAC) as part of a UK-wide operation, involved American company Monsanto.

Professor David Atkinson from the SAC said: "It is a very important verdict for Scottish agriculture and for research in this area.

"We know Scottish agriculture is experiencing difficult times. It needs to be able to explore all the options that are open to it."

Crops destroyed

Giving evidence last year at the trial, Tolmie said he believed the genetically modified crop trials were "evil".

"I would lay down my life to fight against it," he said.

"We had to destroy the field before it destroyed us."

Last year 28 members of the environmental pressure group Greenpeace were cleared of theft and criminal damage after destroying GM crops at a Norfolk farm.

They admitted destroying a six-and-a-half acre field, but argued that they were acting to prevent neighbouring property being damaged by genetically modified pollen.