If a police approved weapon/restraint  (taser in this case) causes a man to die in this fashion, is the police dept liable to a lawsuit, or are they protected under any federal, state or local laws for being sued for accidental death in cases like this?
Bridge City Man Dies After Taser Jolt Sends Him To Cement
ASTRO, the question of whether the police department can be sued is a diffferent one than whether it would ultimately be found liable. Your linked story is out of Louisiana, where the law is wonky anyway, so as far as this particular incident is concerned, I don’t know. (Louisiana’s legal system is broadly historically based on French law, which the rest of the states and the federal systems are broadly historically based on the English common law. Louisiana law is in myriad ways very different than the law in any other state.)
As a general matter, states are protected by the doctrine of Sovereign Immunity, which holds that the governing body may not be sued without its consent. Municipalities enjoy (or do not enjoy) sovereign immunity on the basis of being subdivisions of a state. But if the state has given up sovereign immunity for negligent acts (as most states have), then the municipalities within that state do not have sovereign immunity for such acts, either.
So assuming the municipalities is a legal subdivision of the state, and assuming the state has waived sovereign immunity for negligent acts – yes, the police department can be sued. YMMV if you’re on federal land, an Indian reservation, or in Louisiana. Or have done something other than an allegedly negligent act.