The Dutch judges will not only establish the guilt or innocence of businessman Frans van Anraat, but also determine whether the 1988 massacre of Iraqi Kurds in Halabja amounted to genocide.

The attack, which killed more than 5,000 people in a single day, also features among the preliminary charges against Saddam, who is currently on trial in Baghdad.

Van Anraat is the first person to stand trial on genocide charges for the Halabja attack. He is also charged with war crimes for other Iraqi nerve gas attacks on Kurdish villages in Iraq and in Iran. Prosecutors have asked for a 15-year sentence.

"The mustard gas and nerve gas made with the help of Van Anraat created tens of thousands of victims in Iraq and Iran," prosecutor Fred Teeven said in his closing argument.

According to the charge, the Dutchman acted as a sort of middleman, buying chemicals on the world market and selling them on to Iraq despite export bans then in place.

He supplied included thiodiglycol and phosphorus oxychloride, both described as ingredients for mustard and nerve gases.

Van Anraat, 63, has admitted to selling the chemical components to Iraq, but maintains that he was not aware of the use to which they were put.

However, the prosecution presented several witnesses and documents they said showed Van Anraat knew from 1984 onwards that the chemicals could be used to make poison gas. They also said the Dutchman was the sole supplier of thiodiglycol to Iraq from 1985 to 1988.

Van Anraat, a portly man with a shock of grey hair, refused to answer most of the judges' questions. He appeared seemingly unmoved as several victims of poison gas attacks from Iran and Iraq testified about what happened to them.

He was arrested in Italy in 1989 on a US warrant but later fled to Iraq where he lived for 14 years under a new name given to him by the Iraqi regime, Faris Mansour Rasheed al Bazzaz, meaning "the courageous and intelligent fabric salesman".

He remained in Iraq until US-led forces invaded the country in 2003, and then returned to the Netherlands, Dutch officials said, where he was arrested in December 2004 on charges of complicity in genocide and war crimes.

Fifteen victims of Iraqi poison gas attacked have joined the proceedings against Van Anraat and have demanded damages of almost 700 euros (830 dollars) each, the maximum possible under the applicable law.

The defence has called for the case to be dismissed on the grounds that a trial against the alleged principal perpetrators of the crimes, including Saddam Hussein, is ongoing in Iraq.

Failing that, they have also argued that the prosecution did not present sufficient evidence for a conviction.