In the summer of 2017, dozens of Lyft passengers in Northern Virginia were sent a driver named Yusuf Abdi Ali. He had a high rating on the ride-hailing app, and had made at least 76 trips as a Lyft driver until last September, the company said.

But Mr. Ali, who also drove for Uber, had a secret history: He was a former Somali National Army commander accused of torture and attempted extrajudicial killing, according to a civil complaint that was filed in Virginia in 2004.

This week, a jury in the Federal District Court for the Eastern District of Virginia found Mr. Ali “liable for the torture” of a Somali villager named Farhan Mohamoud Tani Warfaa in the 1980s. Mr. Warfaa, 48, who lives in Somalia and came to the United States to testify this month, was awarded $500,000 in damages. Mr. Ali, who is now in his mid-60s, is unlikely to be able to pay, a lawyer representing him said.

The jury did not find Mr. Ali guilty of attempted extrajudicial killing, one of the two charges in the complaint. His lawyer, Joseph Peter Drennan, said Mr. Ali denied both of the charges.