Drive In Massacre

DriveIn Massacre is a 1977 horror film written and directed by Stu Segall, and cowritten by John F. Goff and George Buck Flower.

That night, the killer strikes again, impaling two lovers while they are making out in their vehicle, and leaving a sword behind. To see if the sword belongs to the missing drivein owner, Germy is brought in to identify it. Germy states that the sword is not apart of the owners private collection, and tells the detectives that the voyeur was at the drivein around the time of the latest double murder, and that he managed to write down the mans license plate number. The plate number is connected to Orville Ingleson, whose home the detectives visit. Orville denies any connection to the deaths, but when a bloody cloth is found in his car, he panics, and tries to make a run for it. Orville is caught, and claims the blood was just from a dog he accidentally ran over, which is confirmed by further analysis, forcing the police to let him go.That evening, the detectives one of them disguised as a woman go to a screening at the drivein, and spot Orville there, even though he had promised to stay away from it. After a customer who had stormed off when his girlfriend refused his advances returns to his car, he discovers that his girlfriend has been beheaded. Leary and Koch rush to Orvilles car, and find him dead from a slit throat. Austin and Germy are brought in for questioning, and Austin antagonizes the detectives, refusing to close the drivein without a court order, and firing Germy. ........

Source: Wikipedia