By Alex Kirby
BBC News Online environment correspondent
The UK government has defied fierce public opposition in deciding to allow GM maize to be grown commercially.
The science has not convinced the opposition
It says it bases its decision on sound science, and promises it will judge all GM crops on a clear case-by-case basis.
But the scientific argument for letting this particular maize crop be grown is so qualified it is open to challenge.
And anti-GM groups, insisting there will never be a case for growing the crops in the particular conditions that apply in the UK, will challenge it.
The first problem stems from the tests conducted on genetically modified maize, beet and oilseed rape, known as the farm-scale evaluations.
The GM maize, unlike the other two crops, outperformed similar fields of unmodified varieties; because it let more weeds flourish, it was judged friendlier to wildlife than conventional maize.
But the chemical used on the conventional crop was atrazine, soon to be banned across the European Union.
There is now debate over how much of its apparent advantage the GM variety would keep when compared with unmodified fields treated with atrazine's less virulent replacements.
More damning than that is the fact that the tests themselves were very limited in scope.
They did not try to see whether genes could flow from GM plants to other crops, or whether their pollen would spread, or what effect they might have on soil organisms.
All they tested was the impact on food sources for wildlife.
And even then the tests did not reveal anything about the nature of genetic modification itself. They showed simply the impact of treating particular crops with specific pesticides in carefully monitored conditions.
Ministers never suggested there should be any tests to see whether GM crops could affect human or animal health, despite the earlier concerns of the British Medical Association.
They relied on the experience of other countries which have found no evidence of harm. That allows their opponents to say absence of evidence is far from evidence of absence.
And recent reports from the Philippines of people living near GM crops suffering respiratory problems, although they remain unconfirmed, will fuel the fears of GM technology.
The government did want to build up a persuasive case for GMs. But some commentators will argue its efforts have been lacklustre, leaving many questions unanswered.
Despite that, there may still be many arguments in favour of GM technology. What is not clear is that it should be used in the UK, where space is limited and the chance of gene-spread is higher than in, say, North America.
Even there, low-level contamination of ordinary crops is reported to be widespread. Its proponents say gene-spread will happen but will not matter.
Britain has in recent years developed a distrust of science; we have become risk-averse, not altogether without reason (remember mad cow disease?). And many people, judging by the opinion polls, believe science still has some way to go to prove GMs are risk-free.