Silencers

The forensic investigation of a crime that involved the use of a firearm is concerned with establishing the type of weapon used. This knowledge helps piece together the circumstances of the crime and can help apprehend those who committed the crime. These ballistic determinations can include obtaining evidence of the use of a silencer.

A silencer, intended to suppress sound, is an attachment to a firearm. Generally, silencers are a six- to twenty-inch steel, titanium, or aluminum alloy barrel addition designed to work with a particular weapon. Silencers have also been constructed from other materials such as plastic soft drink bottles. Nicknamed "whispering death," these devices give a shooter the ability to strike a target with less risk of being noticed. Contrary to popular image, silencers do not completely muffle the sound of a gun, but instead lessen muzzle flash, reduce muzzle noise, and decrease recoil by delaying the escape of gases from the barrel of the firearm.

To an experienced forensic investigator, then relative lack of gunshot residue in a crime involving a firearm can be a clue to the use of a silencer.

Gunsmiths began experimenting with various designs to silence weapons in the nineteenth century. The first person to develop and market a silencer successfully was Hiram P. Maxim, the son of the similarly named inventor of the machine gun. In 1908 Maxim developed a silencer that delayed the release of gases, but he did not market the weapon until making a few improvements. The Maxim Model 1909, released in the year of its name, became the first efficient silencer to be marketed, but the Maxim Model 1910 became the most widely distributed silencer in the United States by capitalizing on an off-center design that allowed it to be used with a weapon's original sights.

Although the military value of silencers quickly became apparent to many observers, Maxim only had the goal of eliminating noise pollution. Many of the first buyers of silencers employed them for target shooting in basements and backyards so that the sound of firing would not disturb others. Silencers also found a market in pest control. Many silencers are still sold for use in eliminating rats, not so much to surprise the rodents, but to avoid the public relations problems associated with shots fired within heavily occupied areas.

The development of a supremely effective silencer has been complicated by many factors. The noise made by the discharge of a firearm has three components: 1) the sounds made by the movement of the parts of the gun; 2) the crack of a bullet passing through the atmosphere at a rate above the speed of sound; and 3) the release of high pressure gases breaking out of the barrel. Silencers only address the last concern, although the use of a heavy subsonic bullet rather than a high velocity bullet greatly adds to sound suppression. High velocity bullets make a noise of their own when traveling through the air outside of the silencer and the substitution of a slower bullet will slow the passage of the projectile through the air, thereby reducing ballistic noise. Silencers that fire regular supersonic ammunition are only a little quieter than those without suppressors. Subsonic ammunition has less power than regular ammunition making it effective only at shorter ranges of up to 600 feet (200 m). Silencers can be attached to most firearms, but they work best as components of purpose built or modified guns.

Silencers are now made for almost every firearm, from fully automatic submachine guns to big bore bolt-action rifles, and the popularity of these weapons is likely to grow.