Explosive properties of pressurized tennis ball construction

Tennis Ball Bombs

One of the concerns of contemporary law enforcement agencies in relation to counterterrorism in the realm of domestic or "home-grown" terrorism are explosive devices improvised from easily-obtainable materials. Tennis balls, racquetballs, and other similar common sports items, for example, have been used increasingly by domestic terrorists. Typically, the balls are cut open, filled with explosive materials such as match heads or explosive powders (i.e. black powder or gun powder) and then resealed. In one such configuration, the ball is equipped with a standard firecracker or an improvised type of fuse. These types of devices have been known to law enforcement for more than a decade and the increasing use of the Internet in the public has increased public awareness of these types of devices. In that regard, "How To" videos and written instructions are readily available on the Internet (1)(2).

Prior Incidents

In Milwaukee, Wisconsin, a police patrol vehicle ran over and detonated a tennis ball bomb in Milwaukee (4). In Portland, Oregon, a dog was killed when it played with a tennis ball its owner had found on the street (7). Two-15-year-old boys were arrested in South Africa after throwing a tennis ball bomb at a school (3). In Fairfield, Connecticut, a tennis ball bomb exploded after it was thrown by a man who found it in the street who started playing catch with it (5). Two Washington State men were sentenced to state prison for possession of a large number of tennis ball bombs, one of which had seriously injured one of the younger brothers of one of the men (6).

Indicators of Potential Tennis Ball Bombs for Law Enforcement

The possession or presence of large numbers of "strike anywhere" matches or (especially) of severed match heads should arouse suspicion. Three boxes of matches is enough to create one bomb. Empty gun powder containers and especially disassembled but non-detonated commercial firecrackers is another potential indicator of the manufacture of improvised explosive devices because the latter provide a means of securing sufficient quantities of gun powder to create a bomb by persons (i.e. juveniles) who cannot ordinarily purchase gun powder, as well as by individuals intending to avoid creating a record of having purchased gun powder. Likewise, the presence of hobby fuses, particularly without other contextual materials suggesting their legitimate use (i.e. model rocketry materials) are another potential indicator of improvised bomb-making activities. Hot glue guns (also outside of contextually appropriate circumstances) are another potential indicator.

Recognizing and Avoiding Detonating Possible Tennis Ball Bombs