Mass. Gen. Laws ch. 38 § 4A
If, after making inquiry pursuant to section four, the medical examiner is of the opinion that death may have resulted from injuries sustained in a motor vehicle accident, and that the death occurred within four hours of such accident, that the deceased was the operator and sole occupant of the motor vehicle, and that no other individuals were involved in the accident, the medical examiner shall submit to the state police laboratory a sample of blood from the deceased in an amount sufficient for chemical analysis if it is obtainable at an autopsy. If such chemical analysis indicates the presence of a controlled substance or alcohol, such sample shall be preserved for no less than one hundred and twenty days from the date the sample is taken to permit an independent analysis. Such independent analysis shall be done upon the written request and at the expense of the next of kin of the decedent. No independent analysis of blood performed after sixty days pursuant to this section shall be admissible as evidence of the level of alcohol or controlled substance in any legal proceeding. The medical examiner shall not be civilly or criminally liable for any action taken in compliance with this section.
Mass. Gen. Laws ch. 38, § 4A