Two elderly women went on trial yesterday for their alleged part in a bizarre and gruesome murder plot that has been compared to the Cary Grant film Arsenic and Old Lace.

Prosecutors claim that Helen Golay, 77, and Olga Rutterschmidt, 75, befriended homeless men in Los Angeles through a church group, put them up in apartments, hired security guards to watch over them, took out life insurance policies in their names, drugged them and then ran over them in a car bought specifically for the purpose.

The car was a 1999 Mercury Sable bought under a fake name. Detectives found human tissue and clumps of hair in its undercarriage.

After the alleged murders - which the authorities initially assumed were hit-and-run incidents - the two pensioners are said to have collected $2.3 million (£1.2 million) in insurance.

The killings were connected only because of a chance meeting between two LAPD detectives. One commented on the strange hit-and-run incident that he was looking into. The other could not believe what he was hearing: he had worked on an almost identical incident six years earlier.

The lieutenant in charge of the subsequent investigation described the case later as “one of the most sinister, evil plots I have ever seen”. It has drawn comparisons with the dark 1944 comedy Arsenic and Old Lace, in which Cary Grant's character discovers that his two aunts kill young men and bury them in the cellar.

The victims of the pensioners' alleged plot were Paul Vados, 73, and Kenneth McDavid, 50, who were killed in 1999 and 2005. At the time of his death, Vados was named in more than a dozen life insurance policies. McDavid was named in 23. In both cases Ms Golay and Ms Rutterschmidt claimed the bodies, saying that the dead men were relatives or close associates.

Prosecutors say that the injuries of the two homeless men were not consistent with those inflicted by hit-and-run incidents: instead of having leg injuries, they both suffered wounds to the head and upper torso, suggesting that they had been lying in the road when they were struck. “This victim [McDavid] was laid down and run over,” Truc Do, deputy district attorney, said at a pretrial hearing.

According to court documents, the defendants had experience of the life insurance industry and used rubber stamps of their victims' signatures to take out multiple policies.

Prosecutors are not seeking the death penalty because the process would take a decade, by which time both defendants could be dead.

Evidence in the case is likely to include DNA taken from the car allegedly used in the killings, prescriptions for drugs that could have knocked out the men and a recorded conversation in which Ms Rutterschmidt accused Ms Golay of taking out too many insurance policies in Vados's name. “You were greedy,” she told her co-defendant. “That is the problem. That's why I get angry ... I was doing everything for you.”

In court Ms Golay and Ms Rutterschmidt make unlikely murder defendants: tiny, frail, grim. Since they were jailed, the women have been in separate cells. Ms Golay has been given thermal underwear and a special diet because of her high blood pressure.

Both the defendants have pleaded not guilty.

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