Despite clichés, and a very depressing finale, this is one of the best-made films of its era and genre.
The strengths of the film include an odd relationship between the two lead cops, who seem loosely based on the two lead cops of the "Lethal Weapon" series, but who (thankfully) never play for laughs, and never really become "buddies" - the young cop is too arrogant, and the older cop has too much experience, which the young cop refuses to acknowledge. The two characters are also brilliantly acted by Morgan Freeman and Brad Pitt (probably his best performance).
There's one odd flaw in the film - about half-way through, I found that I had learned to "expect the unexpected" from the film, which meant that the rest of the film was predictable in a bizarre way - simply decide where the expected move would be, and then expect the unexpected move instead. The most obvious instance of this is in the finale itself, which could be guessed at least 5 minutes ahead of time.
Normally, this would be a formula for disaster - but fortunately, the high quality of the film-making twists the film into an edge-of-the-seat suspenseful waiting game as we watch with horror the one cop's encounter with the insanity of pure evil.
I didn't want to admire this film (to be honest, I dislike Brad Pitt something fierce), but I'm afraid I must - very professionally made, it delivers its promised suspense all the way