The trial of a Tunisian man and his German wife accused of planning a biological bomb attack in Germany started in Dusseldorf on Friday.

The 30-year-old man and his 43-year-old wife were arrested in Cologne last year by anti-terror security officers, who found 84 milligrams of the deadly poison ricin in the couple's apartment. Under German reporting guidelines, the accused cannot be named in full. 

Prosecutors said the raids prevented "the production of a larger quantity of ricin and the building of an explosive."

The raid came after a tipoff from the US Central Intelligence Agency (CIA), whose monitors had noticed the large online purchase of 3,300 castor beans. A small amount of ricin poison is found naturally in castor beans. Officers also found 250 metal balls and wires soldered on lightbulbs.

Failed fighter for IS

The man, a former street vendor, and his wife, an unemployed mother of seven children, met online in 2014 and married a year later. They became supporters of the "Islamic State" terrorist group and the man tried, but failed, to travel to Syria in 2017. The woman published IS material online as a propagandist.

They then researched explosives that could be used "to kill and wound the largest possible number of people," according to prosecutors.

A hamster for testing ricin

The couple in Cologne decided to use poison and chose ricin, which first came to public knowledge as a poison for assassination in 1978 on Waterloo Bridge in London. It was used to kill Bulgarian dissident Georgi Markov, who was jabbed in the leg with a weapon built into an umbrella. Markov was injected with a small pellet containing ricin, and died four days later.

In the following years, ricin was recovered in numerous incidents involving politically and personally motivated attacks, mainly in the US. In October 2018, ricin particles were found in mail sent to the US Pentagon, addressed to President Donald Trump and Secretary of Defense Jim Mattis, among others.

The couple in Germany is believed to have bought a hamster to test the effectiveness of the poison.

Each of the accused faces up to 15 years in jail if convicted. The trial is expected to continue until August.

jm/sms (AFP, dpa)

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