During Prohibition, transporting illegal liquor required secrecy, careful planning, and, preferably, bottles that did not announce their presence by exploding beneath the hood of your automobile.
Roy McKinley was driving through Washington, D.C., on the night of December 3, 1928, when Policeman C. A. Berry of the 12th Precinct noticed him traveling at what appeared to be an excessive speed. Berry stopped the automobile near 18th Street and Rhode Island Avenue NW and began questioning the 21-year-old driver.
Then came a noise that sounded like a gunshot.
The officer listened. Another sharp report came from beneath the hood. Whatever McKinley might have said to explain his driving, there was now something far more interesting happening beside the engine.

Berry lifted the hood and discovered six bottles of liquor hidden inside. According to the policeman, the little stash had originally contained eight bottles. Two had already burst from the heat of the motor, creating the noises that betrayed their presence.
McKinley was arrested and faced charges of transporting and possessing liquor.
Bottles Blow Up in Auto as Bluecoat Talks to Driver

WASHINGTON, D.C. — His own auto turned against him last night and Roy McKinley, 21, faces charges of transporting and possessing liquor.
Policeman C.A. Berry, 12th Precinct, halted McKinley’s car at 18th Street and Rhode Island Ave. NW, because he thought McKinley was going too fast.
As he talked to the driver, Berry heard a sound resembling a gunshot. He listened and it was repeated, apparently from under the engine hood.
He lifted the hood and found six bottles. There had been two more, he says, but the heat of the motor exploded them.
Source: The Washington Daily News. Washington, D.C. December 4, 1928.
