In a way the show highlights how inept the police is - it seemed pretty straightforward to be able to catch the guy, if they knew he was from Bihar and had served time at Tihar earlier and had a grudge against Balbir the constable. Here are some obvious issues to a common man's eyes:
1. Unable to follow most obvious clues like victim's name tattooed on the arm.
2. No procedure to contain the crime scene to prevent contamination. In one case, they don't even have a knife to cut ropes and the killer himself obliges.
3. To look for a head dumped in the river, you need divers - you can't go on a leisurely boat ride and find something at the bottom of the river by just looking at the surface.
4. Do they not have Luminol or something to highlight blood stains in the room, if the guy did all this butchering in a 1 room apartment.
5. Seems like they did not bother to look at images from the killer's camera - since the documentary claims that these are available for the first time.
6. They strung along a victim's family by just sending them on a merry go around and charging them for bribes.
Somewhat inept story line - seems to warrant an investigation into police practices at the very least.