“He kept the lights off, because he didn’t want anyone to see in,” says John L. Barker of the rooms his father rented to test a radar system he was making for the U.S. military. John L. Barker Sr. — then an engineer at Automatic Signal Company — had been working on traffic lights in the 1930s, but during World War II, he dedicated himself to military research. “He pointed the machine out a window, and he tested it on cars that drove through an intersection.” Barker was about 8 years old at the time and admits that his memories are hazy. “I have no idea why I was even involved,” he says.

When the war ended, Barker Sr. experimented with a new, peacetime application for the technology. He would pack the radar equipment in the trunk of his car and play cop on the Merritt Parkway. “He would pull off the road and open the trunk so that the equipment faced traffic,” his son says. At the time, police officers had no precise way to clock a car; Barker knew that his device could change the rules of the road.

In 1947, the town of Glastonbury, Conn., deployed Barker’s machine on Route 2, creating what was perhaps the world’s first speed trap. “This is the latest scientific method,” a police captain named Ralph Buckley told a reporter in 1949. “It removes the possibility of human error.” And he added, “Any speeder who gets caught will have to argue with a little black box.”

Argue they did. In 1955, a Connecticut woman contested her speeding ticket in court, claiming that the radar must have been broken on the day it registered her blowing through a 25-mile-per-hour zone. Her lawyer further protested about a “lack of fair play” on the part of the police for pointing this high-powered, wartime technology at drivers. Barker was called in as an expert witness. He insisted his radar machine didn’t lie. (According to his son, he frequently appeared in court to defend his invention.)