Continuity mistake: When Gordon jumps out of the window, shards of glass breaks off, flying all around him as he jumps. In the next shot all the shards have just disappeared. (01:10:05)
Continuity mistake: When Trish grabs the TV to hit Jason with, the big lamp gets knocked to the floor. Moments later as they leave the room, the lamp is back up to standing. (01:16:20)
Continuity mistake: After Trish jumps out of the window, the position of her feet and legs, and the planks of woods around her, change between shots. (01:18:15)
Continuity mistake: When two of the teens are dancing to the rock music, one boy walks over, changes the record and then places a vinyl record on top of a box. In the next closeup the vinyl record he placed down has gone. (00:34:35)
Revealing mistake: When Trish jumps out the window and falls to the ground you can see her using a body suit covering her from her hips and down her legs. (01:18:15)
Continuity mistake: After Tommy slices Jason in the head with the machete, he picks the machete up, and in this shot his shirt is dry. In the next shot when Trish goes over to hug him, his shirt is wet, then dry again. (01:22:00)
Continuity mistake: When the six teens are driving along in the car singing, between a wide shot and closeup of the car, the road and scenery behind them changes. (00:15:35)
Revealing mistake: When Trish jumps out through the window, rolls off the deck, and lands on the ground below, she obviously lands on a mat or some other protective device covered to look like mud. It jiggles like jelly in a perfect square when she lands on it. (01:18:15)
Continuity mistake: When Sara goes into the second floor bathroom to dry her hair, there is a bench in the hall. Later, when Jason chases Trish upstairs, the bench has moved across the hall. (01:06:30)
Continuity mistake: When Tommy is pretending to sleep when his mom comes into the room, he is on his stomach when she pulls the blanket over him. In the remaining shots starting with when his mom is closing the blinds, Tommy is suddenly laying on his side. (00:51:15)
Continuity mistake: Trish swings the machete at Jason, and knocks his mask off. In a behind shot she holds the machete with both hands. In the next shot she only holds it with one. (01:21:05)
Continuity mistake: Trish swings the machete overhanded, but in the next shot she knocks Jason's mask off underhanded. (01:24:25)
Revealing mistake: When Tina is thrown out the window you can see the roof of the car is partially damaged and very flexible when she hits it. (00:59:25)
Continuity mistake: When Jason kills Doug in the shower, there are two red lines on his hockey mask, under the eyes. However later, when Jason bursts through the window and grabs Tommy, the lines are gone. (01:05:10 - 01:14:45)
Continuity mistake: Jason slashes Jimbo in the face with a cleaver. It then cuts to another scene happening elsewhere. Then when it cuts back to the scene with Jimbo, Jason now has a large bloody knife instead. (00:58:30 - 01:01:20)
Continuity mistake: Right before Jason slits Axel's throat, we see him grabbing Jason by his elbow. When it cuts from a shot above we see him holding Jason by his wrist. (00:13:25)
Continuity mistake: When Sam asks Sara to come into the water, Sara says no. Then Sam says "Then I'll go under water and stay there until you do", while placing her hands on the edge of the pier. When it cuts to a close-up of her she is resting her arms on the pier instead. (00:29:20)
Continuity mistake: When Trish is inching by Jason lying on the floor, in one shot she steps over his arm and her feet are near his shoulder, then in the next shot it shows her stepping over his arm again. (01:17:10)
Continuity mistake: When Tommy and Trish are hiding in a room, they sit down on the floor and Tommy grabs a chair in front of him. When it cuts the chair lies on the floor. (01:15:25)
Continuity mistake: In part 3, Jason was stabbed in the hand and leg yet there are no wounds or damage to his clothes.
Answer: Jason killed her. There was a scene shot but never shown where Trish discovers her mom's body.
SAZOO1975