The Church is pretty consistent when it comes to life.... the killing of the unborn and capital punishment are both against the churches teachings.

It also would seem that manslaughter was a possible charge for the crime in 1969.

From Wiki----


Under Massachusetts law Boyle, having found "probable cause" that Kennedy had committed a crime, could have issued a warrant for his arrest, but he did not do so.[33] District Attorney Dinis chose not to pursue Kennedy for manslaughter, despite Judge Boyle's conclusions.