How Police Chases Work

The main piece of equipment that a police officer relies in a pursuit is the police car. Modern police cars are special "police interceptor" versions of large sedans made specifically for police work by auto manufacturers. The most common police car in production today is the Ford Crown Victoria, although police officers also use Chevrolet Impalas, Chevy Tahoe SUVs, Dodge Intrepids, and Jeep Cherokees. The Italian police even use a Lamborghini.

There are quite a few differences between a police car and the civilian version of the same car. Police departments often opt for higher horsepower engines, not only because police cars weigh more, but for the acceleration and speed needed to catch up to criminals in a high-speed pursuit. Police cars receive harsh treatment on a daily basis, idling for a long time and then roaring off at high speed. To cope with the extra heat, transmission coolers and oil coolers supplement heavy-duty radiators. Alternators in police cars can crank out up to 130 amps to run lights, sirens, radios and other equipment [ref]. There are other differences related to suspect transport, such as metal reinforced seat backs (to prevent stabbings from behind) and vinyl covered bench rear seats for easy cleanup.

Flashing lights and loud sirens alert civilians that a police car is coming at high speed. The lights evolved from taillights in the 1930s, and were originally mounted on fenders. By the mid-70s, roof-mounted lights of varying colors were placed within an aerodynamic enclosed light bar [ref].

There are several systems that police can deploy ahead of a chase to disable the fleeing vehicle. The most common are spikes that puncture and deflate the tires. These are generally mounted on a bar or flexible cable, and deployed across the road. Models available include the Magnum Spike, Stop Sticks and the Stinger.

A method often seen in movies that police actually use is the police roadblock. By parking several cars across the road, or using some other form of barrier, police can slow or stop a criminal involved in a chase. Even if the suspect avoids the roadblock, it usually diverts their course or forces them off road, where they can't drive as fast and their car might be damaged.

More elaborate (and often experimental) systems try to disable the car's electrical system. The High Speed Avoidance Using Laser Technology (HALT) system would allow officers to cut the fuel supply to the engine by simply firing a laser at the car, gradually slowing it. Only vehicles equipped with a special microchip could be disabled, however [ref]. Another company is developing a microwave gun that would overload the electrical systems and computers in a car.

If officers have air support, they don't even need to stay within sight of a fleeing suspect. Police helicopters can maintain visual contact at greater speeds and without having to worry about terrain or road conditions. When equipped with infrared or night vision cameras, they can even carry on a pursuit at night or through heavy undergrowth.

In the next section, we'll follow a police pursuit and learn about the decisions involved.

Let's examine the various decisions that an officer has to make when starting, engaging in and finishing a pursuit. Suppose an officer is patrolling a highway when he spots a car passing him at faster than the posted speed limit. He accelerates and tails the car, but doesn't turn on his lights and sirens yet. He uses his radio to call in the license plate numbers and find out if the car is stolen or if there are warrants out for the owner. Once he gets this information, he hits the lights and sirens to pull the driver over for speeding. At this point, the driver speeds up, trying to escape.

The police officer has an important decision to make -- should he pursue or not? He must consider many factors when making this decision. The most important is the nature of the crime. If the car's tag came back clean, then a pursuit would probably not be justified. But if a report came back that the car was stolen at gunpoint, or had been used in an armed robbery, then the officer would have reason to believe the driver posed a serious danger and needed to be stopped.

He would also consider road conditions. If the owner of the car is wanted for tax evasion, he or she doesn't pose an immediate danger, but should still be arrested. On a clear day with little traffic, a pursuit could be justified. On a rainy night when the streets are clogged with traffic, or in the afternoon when school buses are dropping off children, he might have decided that it was not worth the risk.

Department policy comes into effect in making a pursuit decision. For example, departments in the Des Moines, IA area must limit "the number of police cars chasing a suspect car to three, regardless of the number of agencies involved. Officers also must take into account the time of day, road and weather conditions, and the nature of the offense. A supervisor must approve continuation of a pursuit" [ref]. In Washington D.C., pursuit is justified only if the suspect has engaged in a violent act or "someone could be seriously hurt if the suspect was allowed to escape" [ref]. Orange County, FL has one of the most restrictive pursuit policies in the United States. In the year following enactment of that policy (2005), felonies in Orlando declined compared to the previous year [ref]. Officers will typically stay in radio contact with a supervisor throughout the chase, keeping the supervisor apprised of the situation. If it gets too risky, the supervisor can call off the chase. It's important that someone not directly involved in the chase make these decisions, since they can keep a cooler head and be more objective.

The Pursuit Intervention Technique

The use of spike strips and roadblocks offer some possibilities for ending chases safely, but officers often rely on something known as the Pursuit Intervention Technique, or PIT (also called Tactical Vehicle Intervention). The Pursuit Intervention Technique is a method of striking the fleeing vehicle in the rear corner, just behind the rear wheel. This will put the car into a spin from which the suspect will not be able to recover [ref]. However, this is a potentially dangerous move, since it makes the suspect lose control. The road must be clear of traffic and the surrounding area clear of pedestrians before an officer can safely pull off a PIT maneuver.

It is very rare for police officers to try to shoot out a fleeing suspect's tires, or to shoot at a moving vehicle at all. The risk of accidentally shooting a bystander is too great. Shooting out the tires is a last resort, if all other attempts to disable the vehicle have failed.

Once an officer disables the vehicle, the suspect may flee on foot, or he or she might be incapacitated. At this point, an officer's suspect apprehension training takes over.

In the next section, we'll explore the legal ramifications of a police chase.

Very few laws specifically control police pursuits. Instead, police department policies dictate pursuit restrictions. Legally, police officers have a right to pursue. Even if they fail to follow department policy, they probably won't have broken any laws, but they might suffer consequences within the police force.

According to National Highway Traffic Safety Administration data, there were 365 deaths resulting from crashes during police chases in 2001. 140 of those killed were innocent bystanders [ref].

Who is liable if a chase results in property damage, injury or death? It depends on the laws of the town, city or county in which the chase occurred. The American common law rule is sovereign immunity -- that is, government officials and institutions are not liable for any damages that occur while they are in the course of their government duties, no matter how negligent their actions. However, most municipalities have written laws that supersede this sovereign immunity. These laws make individuals immune from liability, but claimants can still sue institutions. So if a police car injures your family during a chase, you can't sue the officer driving the car, but you can sue the police department and its municipality. Again, liability will vary from place to place. California is known for a law that gives police departments almost complete immunity in pursuit situations.

A common myth about police chases is that it is illegal for a police officer to drive above the speed limit and disobey traffic signs unless the lights and sirens are on. In fact, police officers can legally pursue at high speeds even if they don't turn on lights and sirens [ref]. However, department policies may contradict this precedent.

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