Under G. L. c. 90, § 24G(b), somebody who operates a car or other vehicle recklessly or negligently and endangers the lives of others, and thereby causes another's death, can be convicted of homicide by a motor vehicle. The punishment is imprisonment in jail or a house of correction for a minimum of 30 days and a maximum of 2 1/2 years, or a fine of $300-3,000, or both of these.
In Commonwealth v. Gallien, the defendant was convicted of motor vehicle homicide by negligent operation. The evidence showed the defendant didn't stop the tow truck he was driving, resulting in a crash with a Honda Civic stopped at a red light. The collision killed a passenger in the rear-seat of the Honda.
The judge precluded the defendant from presenting evidence about modifications made to the Honda. The court explained that in criminal cases, a victim's contributory negligence, even if it is a big part of the cause of a homicide, doesn't excuse the defendant for also causing the victim's death. To the extent that the defense's goal was to show the victim was also negligent, excluding the evidence was proper. On appeal, however, the defendant argued that the modifications evidence should have been admissible not to show the victim's negligence, but to show that the driver's actions were an intervening or superseding cause of the victim's death. The driver was a third party, not the victim.