Lord Melchett's victory will prove to be a defeat for scientific truth

Yesterday's stunning acquittal of Lord Melchett and the Greenpeace protesters who sought to disrupt the genetically modified crop trials in Norfolk is a disaster for the Government - and a disaster for the scientists who wanted to find the truth. It now seems unlikely that any further trials will be able to go ahead. It would be natural if farmers were so frightened by the prospect of being targeted that they refused to host the GM trials.

Yesterday's stunning acquittal of Lord Melchett and the Greenpeace protesters who sought to disrupt the genetically modified crop trials in Norfolk is a disaster for the Government - and a disaster for the scientists who wanted to find the truth. It now seems unlikely that any further trials will be able to go ahead. It would be natural if farmers were so frightened by the prospect of being targeted that they refused to host the GM trials.

The whole point of the trials was to find out what effect the GM crop trials would have on the environment, including the effect on insect life and on other animals. The trials took place with an open mind; the protesters have shown no such openness. If the trials cannot go ahead because of the threat or fear of sabotage, scientists will be unable to establish whether or not there is a genuine threat. We are, in short, left in complete ignorance.

The issue of the crop trials must be seen quite separately from questions about health concerns in connection with genetically modified foods. GM food has undergone extraordinarily elaborate testing procedures - much more elaborate than many other types of food, including the endlessly praised organic food. By all scientific markers, GM foods are as safe as can be. They can be placed on shelves for consumers to decide whether they want them.

The issue of potential damage to the environment is, however, a different issue. The more efficient we are at producing crops which only humans can eat, the more certain it becomes that other animals living in the countryside will suffer. An insect that is a pest for farmers is essential food for a skylark.

Thousands of acres of GM crops are grown in the US, and this is often used as an argument to show that GM crops do not damage the environment. However, in America the wilderness areas are divorced from the farmland areas. In this country, by contrast, wildlife and farmland mingle on an intimate scale.

The potential threat must therefore be recognised as much more serious in Britain than it is in America. That is not an argument for not carrying out the trials. On the contrary, it makes it all the more imperative that we understand the rational and scientific arguments connected with GM crops.

The farm-scale crop trials that the Government introduced were due to expand enormously over the next three years. Already, trials of winter oilseed rape are now taking place on 25 sites. GM crops are planted in one part of the site, while the rest of the site is planted with equivalent trials of non-GM crops.

Even before yesterday's decision, some farms which had signed up for these trials pulled out because of fear of direct action. Yesterday's verdict seems certain to accelerate that process. It is not a question of whether the farmers themselves believe that there is a problem with the crops. The threat of Greenpeace protesters would be enough to frighten them off.

If juries refuse to convict people who deliberately sabotage GM crops, then farmers would hardly welcome the invitation to be involved in such trials. Greenpeace has been expert at getting publicity for its cause. Now, it seems, Greenpeace and its lawyers are also expert at persuading a jury of the rightness of their cause. But knowledge is the loser; Greenpeace has bolstered the prejudices of those who do not wish to know the truth. It has done no service to our need for knowledge.