According to the Tuesday's ruling, Alexander Rabinovich, 22, supplied Eliran Golan, the main suspect in the case, with the explosives that were used to manufacture the homemade bombs.
Rabinovich was convicted of four counts, including assisting an attempted murder, conspiracy, arms dealing and arms manufacturing. He faces up to 20 years in prison.
Golan, the main suspect whose trial has been postponed until a ruling is made on his mental capacity to stand trial, is accused of targeting Arabs in the city of Haifa, including a bomb placed in a mosque, and an attempt to kill lawmaker Isam Makhul.
A small bomb exploded under Makhul's car in October 2003, without causing injuries, when his wife started the vehicle. Makhul was not in the car.
Three people were slightly wounded in the other attacks, including a small boy who found one of the bombs.