A London cab driver accused of sexually assaulting more than a dozen female passengers plied them with drug-laced drinks to make sure they couldn't defend themselves, a prosecutor alleged Wednesday.

John Worboys, 51, attacked 14 women over a period of a year and a half until he was arrested last February, prosecutor Johannah Cutts said. Police said Worboys targeted women who had been drinking and sometimes dropped off their friends before attacking the passenger left behind.

"Having each girl alone in his cab was a start but this defendant wanted to ensure that there would be no struggle, no difficulty in achieving this aim. How did he do that? He did it by drugging them," Cutts said.

She said that Worboys, who was licensed to drive one of London's famed black cabs, allegedy told the women he had won money at a casino or through the lottery and then asked if they would share a celebratory drink with him. Cutts said Worboys kept the drinks in his cab and laced them with sedatives.

Worboys denies the 23 charges against him, including rape, sexual assault and administering a substance with intent.

London authorities have repeatedly urged people to avoid using unlicensed cabs, but the city's licensed black cabs — with their classic shape and roomy interior — are advertised as a safe way to get around. Black cab drivers are tested on their knowledge of London's streets and go through criminal background checks before getting their licenses.

Worboys was arrested and charged after one of his alleged victims came forward last February. Police said they were then able to link that case to several others. Some other women then came forward after hearing about the case.

Worboys could face a life sentence if convicted. The trial is expected to last several weeks.