FORISTELL • The silver pickup was swerving all over the interstate.

First, it drifted to the right, onto the rumble strip, and then it entered the shoulder of eastbound Interstate 70. It swayed back to the left as it approached the Foristell overpass.

A Foristell police officer eased his cruiser behind the 2009 GMC Sierra and activated his emergency lights and siren.

“He thought he had a drunk driver,” said Police Chief Douglas G. Johnson.

Instead he had an underage driver, a 13-year-old boy.

“When the officer asked the driver for his license, he said, ‘I don’t have one,’” Johnson said. “Instead the passenger handed over his license and registration.”

The passenger was David Mooneyham, the boy’s father.

Mooneyham, 46, had too much to drink, so he told his son to drive home, police said.

The two had been at the boy’s baseball game Saturday at the Bridgeton Athletic Complex.

The boy, who was driving for the first time, missed the exit to his home in Wentzville, so he turned around in Wright City about 7:45 p.m., police said.