Massachusetts Civics Classes (Highschool Level)

A case my highschool resource officer, now a booking sergeant for state PD, told us about, in civics class?
A man was cleared of murder charges, because his wife was a missing person, the state trooper searched the guy's trunk and found the carved up corpse, beginning the investigation, but he didn't have probable cause to search, the suspect was nervous.
He needed an actual probable cause, so the dead body was dismissed, and anything produced in investigation by it.
It was a nervous husband and a missing person case, how is that murder?
Motion to dismiss the charge.
Granted.
Can't appeal it, that's double jeopardy. You can only appeal on a guilty verdict, not a not guilty verdict.
Not a federal crime either, didn't cross province lines. Or a county case, for local ordinance, the arrest occurred on the freeway, that's a state case for municipal capital.