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WASHINGTON - A parking ticket tripped up the Son of Sam, the Long Island sniper was found because of a burglary, and Oklahoma City bomber Timothy McVeigh drove too fast on his way out of town.

In mass-murder history, it’s often the killers’ own mistakes that are their undoing.

Washington-area police are hoping the same kind of break will lead them to whoever is responsible for a rash of sniper shootings that has killed seven people and injured two since Oct. 2.

Whether a killer takes out one person or many people over time, crucial mistakes usually are made, said Tod Burke, associate professor of criminal justice at Radford University.

Take David Berkowitz, the self-described Son of Sam who terrorized New York City for more than a year in the mid-1970s, killing six people and wounding seven with a .44-caliber revolver.

His mistake was parking illegally - and getting a $25 ticket that led to his arrest.

“Here’s this guy that was taunting the police with letters and everything else and how does he get picked up? Through a parking violation,” Burke said.

A Brooklyn woman walking her dog on the night one of Berkowitz’s victims was killed said she saw a car in front of a fire hydrant being ticketed and the owner carrying something in his outstretched right hand. She heard four gunshots, one right after the other, as she raced home in fear.

She did not notify police about what she had observed for several days.

When she did, police began tracing all cars given summonses in the area of the murder, and came up with Berkowitz’s name.

Berkowitz is serving six consecutive 25-years-to-life sentences and was denied parole earlier this year.