The Hill Valley Police Department was the primary police force in Hill Valley throughout its later years. Prior to the department's creation, the county sheriff handled matters of law enforcement.
In 1955, a Hill Valley policeman was seen walking a beat around Courthouse Square on Saturday morning, November 5. On the night of Saturday, November 12, the officer investigated Doc Brown's "weather experiment" and asked whether he had a permit.
In 1985A, the Hill Valley Police Department, which was owned by Biff Tannen, was corrupt and had their hands on a military tank. A wrecked police car — with the license plate number 766825 — was abandoned in the streets of Lyon Estates, while three police cars sped past the entrance to the neighborhood with strobe lights flashing and sirens sounding as Marty ran towards Courthouse Square. A NO TRESPASSING sign from the Hill Valley Police Department was also seen attached to the barbwire-topped chain-link fence surrounding the burnt-out remains of Hill Valley High School.
In 2015, the force included units that were comprised of females. Three police officers on motorcycles responded to the destruction of the foyer of the Courthouse Mall, and the female officers arrested Griff's gang.
Officers Foley and Reese of Unit N11-11 took an unconscious Jennifer Jane Parker McFly back to her home in Hilldale in their hover converted squad car, after having used an identa-pad to verify her identity and where she lived. They wore peaked caps which featured an electronic readout on the hatband — where the police badge would be normally — displaying messages such as Do you know where your children are?, Look before you gleek!, Do not covet thy neighbor's thumb! (no doubt a warning to potential thumb bandits), and Have you bought your tickets to the policeman's ball?
Behind the scenes
- One of the scenes filmed for Back to the Future, but left on the cutting room floor, explained that the "permit" that Doc found in his wallet was actually a fifty dollar bill, which the police officer took in return for "looking the other way". The explanation (that there never was a permit) clears up a mystery for some viewers of the film, since, if Doc had obtained permission for setting electrical wire downtown, he could be blamed for the damage to the clock (and possibly even forced to pay, from his wealth, for its repair, which would then create a paradox).
- Fortunately (and sometimes not), for Doc and Marty, Hill Valley's law enforcement appears to be ineffective regardless of the year. In 1885, Doc is not linked to the theft or destruction of Locomotive 131. In 1931, Officer Danny Parker becomes corrupt and frequently intoxicated. In 1955, the police are not present when Biff drives his car recklessly through Courthouse Square, nor when Marty drives at 88 miles per hour toward the square, nor does Doc have any further problem in taking down the wiring for his experiment. In 1985, the police officer does seem to notice Marty skateboarding on the back of his car. In 2015, the police stand and watch while Griff's gang prepares to injure Marty, whose hoverboard is stranded over the pond at the Courthouse Mall; a response comes only after the front entrance is destroyed.
- The department is at its nadir, however, on the weekend of October 26, 1985. Not only were Doc and Marty able to drive away from the Lone Pine Mall (with a van full of stolen plutonium) only minutes after gunfire, a high speed chase, and the crash of a van into a Fox Photo kiosk, they were also able to drive away the DeLorean time machine, which had been left by Marty at Courthouse Square, several yards away from the destroyed front entrance of the Assembly of Christ building. The destruction of the DeLorean on the railroad tracks went uninvestigated on Sunday morning (although in Timeline 2, Marty was apparently prosecuted after his collision with a Rolls-Royce). The novelization does include mention of sirens approaching as Doc and Marty slip away from the mall.
- The scene where Marty comes across the burnt-out remains of Hill Valley High School in 1985A appeared only in a deleted scene from Back to the Future Part II, but was reinstated for the novelization.