Turner & Hooch (1989)

Detective Scott Turner has three days left in the local police department before he moves to a bigger city to get some 'real' cases—not just misdemeanors. When Amos Reed is murdered, Scott sets himself on the case, but the closest thing to a witness to the murder is Reed's dog, Hooch, which Scott has to take care of—to avoid Hooch being 'put to sleep'.