begining of csi lab

Two men, Tom and Bob were at a party and got into an argument. Tom said that Bob had stolen money from him. Both left in their cars still yelling at each other leaving the parking lot. Later Bob was found dead in his car from a crash. Tom had run into his car from behind at an intersection. Bob was waiting in the intersection to turn left and Tom said he didn’t see him and tried to stop but didn’t have time to stop. Many think Tom purposely hit him at full speed. At impact the two cars locked together and continued to slide. If Tom had seen him and tried to stop his speed upon impact would have been 4.5 m/s but if he hit him at full speed his speed upon impact would have been 18 m/s.