The 31-year-old defendant, Nikolai H., was found guilty of murder, three counts of attempted murder, and dangerous interference with traffic on Wednesday.

On March 23, 2008, Nikolai H. threw a six-kilogramme piece of wood from a bridge over the A29 motorway near Oldenburg out of what he said was “general frustration.” The wood broke through the windshield of a passing car, killing the 33-year-old woman in the passenger seat. Her husband and children were not harmed in the accident.

Nikolai H., who has been described a “seriously addicted to drugs,” was arrested in May 2008 and confessed to the crime, though he later retracted his statements.

Mobile phone records show he was on the bridge at the time of the murder, and authorities believe the wood came from near his home.

The judge expressed his empathy for the woman’s husband, telling him his calm reaction to the accident at the time saved him and his children in what he called a “gruesome, senseless crime.”

The defendant’s lawyer said he would appeal the case.