Good to see that the opinions here about SHALLOW GRAVE are consistent: It's a better movie than it probably had to be. An opening teaser segment with a co-ed being butchered in a shower is a dead end, or rather an attempt to mollify audience members who expect films with such titles to feature such content. Once that's out of the way and the misleading "bimbos off to party on spring break" setup is complete what you are left with is indeed one mean movie.
It's actually more of a hicksploitation thriller than an outright horror film though the central character is indeed a psychopath. He's a small town sheriff who's used to getting his way and has no scruples against planting incriminating evidence, violating people's Constitutional rights, or resorting to outright murder when convenient for his needs. Four young ladies on a road trip happen upon him murdering a local squeeze and find themselves powerless to escape his clutches. The film is mean spirited, unforgiving, knows that the scenario being presented is chillingly possible & has fun playing with our fear of ending up in a similar jam. Check it out.