A German man has been sentenced to life behind bars after poisoning his co-workers’ sandwiches, leaving one in a coma and two others with serious kidney damage.

The 57-year-old man, identified only as Klaus O because of German privacy rules, was caught on CCTV putting a suspicious powder on a colleague’s sandwich at a business in the city of Schloss Holte-Stukenbrock.

When authorities searched his home, they found a primitive chemistry laboratory in the basement and a substance that Judge Georg Zimmermann described as “more dangerous than all combat agents used in World War Two”.

Two of the defendants’ colleagues, a 27-year-old man and 67-year-old man, suffered chronic kidney damage from poisoning with lead and cadmium. Both men face a heightened risk of cancer.

A 23-year-old trainee fell into a coma after ingesting mercury and now has permanent brain damage.

The worst ever inflight meals Show all 8 1 /8 The worst ever inflight meals The worst ever inflight meals Cockroach curry A cockroach was found in an Air India breakfast meal. Twitter/Manoj Khandekar The worst ever inflight meals Apples and pears Avianca's idea of a vegetarian meal was an apple and a pear on board one flight. Twitter/Steve Hogarty The worst ever inflight meals Chicken sandwich Emirates served this disappointing Cajun chicken and cheese sandwich on a flight to Dubai Paul Carlin The worst ever inflight meals Gluten-free banana Martin Pavelka was handed this banana, complete with "gluten-free" label, as his inflight meal on an ANA service from Tokyo to Sydney. Martin Pavelka/Evening Standard The worst ever inflight meals Mushroom sandwich Oman Air's finest: presenting something approximating a mushroom sandwich on a flight to Heathrow. Nick Boulos The worst ever inflight meals Raw vegetables Aegean Airways served up some raw pepper and carrot sticks as its veggie option on one flight. musterknabe The worst ever inflight meals More cockroaches An Air India passenger wasn't impressed when she found this in the business class lounge. Twitter/Harinder Baweja The worst ever inflight meals Leftovers Not everyone turns their nose up at plane food - this Urumqi flight attendant was suspended after a video of her eating leftovers went viral. Viral Press

The defendant refused to speak during his trial and his motives remain unclear – but prosecutors believe he wanted to see his colleagues’ physical decline.

The judge said the court considered the crimes to be as serious as homicide, according to German news agency dpa.

He found the defendant guilty of attempted murder and sentenced him to life in prison.