Ninja rocks is a colloquial term for an

improvised weapon An improvised weapon is an object that was not designed to be used as a weapon but can be put to that use. They are generally used for self-defence or if the person is otherwise unarmed. In some cases, improvised weapons are commonly used by at ...

or tool consisting of the extremely sharp

porcelain Porcelain (), also called china, is a ceramic material made by heating Industrial mineral, raw materials, generally including kaolinite, in a kiln to temperatures between . The greater strength and translucence of porcelain, relative to oth ...

ceramic A ceramic is any of the various hard, brittle, heat-resistant, and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcela ...

shards recovered from smashing or crushing the

alumina Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly ...

insulator of a commercial

spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...

. When thrown, ninja rocks are known to exploit the tensile stress present in the side windows on most cars in order to instantly shatter them, providing a quick and quiet alternative to other window-smashing methods and making ninja rocks ideal for emergencies or " smash-and-grab"

auto Auto may refer to: Vehicles * An automobile, or car * An autonomous car, a self-driving car * An auto rickshaw Mechanisms * Short for automatic * An automaton * An automatic transmission Media * Auto (art), a form of Portuguese dramatic play * ...

burglaries, having been used in the latter function since at least 1995. They have no traditional association with the ''

ninja A , or was a spy and infiltrator in pre-modern Japan. The functions of a ninja included siege and infiltration, ambush, reconnaissance, espionage, deception, and later bodyguarding.Kawakami, pp. 21–22 Antecedents may have existed as ear ...

'' or ''

ninjutsu , and are terms for the techniques and skills used by spies and scouts in pre-modern Japan known as ninja. Some of these techniques are recorded in ninja scrolls, some which have been published and translated. The study of these scrolls have c ...

'', only being named such due to their "silent but deadly" function in burglaries and a superficial resemblance to the

shuriken A is a Japanese concealed weapon used by samurai or ninja or in martial arts as a hidden dagger or '' metsubushi'' to distract or misdirect. History The origins of the ''bo-shuriken'' in Japan are still unclear, despite continuing researc ...

stereotypically used as a throwing weapon by ninjas.

Functionality

Ninja rocks take advantage of the physical properties of tempered glass, disrupting surface compressive stress and causing the glass to shatter.

Tempered glass Tempered or toughened glass is a type of safety glass processed by controlled heat treatment, thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into Compression (physics), comp ...

, which is used for the side windows of most vehicles, is manufactured with an extremely high surface compressive stress and high internal tensile stress. This gives it strength and durability against shocks and blunt impact. When the glass breaks (such as in a serious vehicular collision) the internal stresses present in the pane cause the entire pane to shatter into thousands of tiny pieces. This reduces the risk of laceration one might otherwise face when using 'normal' glass, and is an essential safety feature in vehicular design. It is these physical stresses designed into tempered glass which make it vulnerable to ninja rocks. Made of shards of

aluminium oxide Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several Aluminium oxide (compounds), aluminium oxides, and specifically identified as alum ...

ceramic, ninja rocks are very hard, and very sharp. When thrown at tempered glass, the ninja rocks' sharp, hard point focuses impact energy into an incredibly small area without blunting. This disrupts the glass surface compressive stress at the point of impact, subsequently releasing the internal potential energy within the stressed pane, shattering the glass. To be effective, a ninja rock needs to be sufficiently sharp, impact the glass on that sharp point, and impact it with sufficient force. Thrown ninja rocks may often fail to shatter tempered glass if one of these conditions is not met. Ninja rocks are ineffective against

windshield The windshield (American English and Canadian English) or windscreen (Commonwealth English) of an aircraft, car, bus, motorbike, truck, train, boat or streetcar is the front window, which provides visibility while protecting occupants from t ...

s, as these are made of a laminated type of

safety glass Safety glass is glass with additional safety features that make it less likely to break, or less likely to pose a threat when broken. Common designs include toughened glass (also known as tempered glass), laminated glass, and wire mesh glass (als ...

, and designed not to shatter.

Legal status

United States of America

California

California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...

, since 2003, ninja rocks have been explicitly listed as

burglary Burglary, also called breaking and entering (B&E) or housebreaking, is a property crime involving the illegal entry into a building or other area without permission, typically with the intention of committing a further criminal offence. Usually ...

tools, and their possession with intent to burglarize is a

misdemeanor A misdemeanor (American English, spelled misdemeanour elsewhere) is any "lesser" criminal act in some common law legal systems. Misdemeanors are generally punished less severely than more serious felonies, but theoretically more so than admi ...

punishable by up to six months in

county jail A prison, also known as a jail, gaol, penitentiary, detention center, correction center, correctional facility, or remand center, is a facility where people are imprisoned under the authority of the state, usually as punishment for various cr ...

and/or a

fine Fine may refer to: Characters * Fran Fine, the title character of ''The Nanny'' * Sylvia Fine (''The Nanny''), Fran's mother on ''The Nanny'' * Officer Fine, a character in ''Tales from the Crypt'', played by Vincent Spano Legal terms * Fine (p ...

of up to $1000. Legal records do not use the phrase "ninja rocks", preferring more precise phrases such as "

or porcelain spark plug chips or pieces". Until 2003, "burglary tools" in California did not include devices to break

glass Glass is an amorphous (non-crystalline solid, non-crystalline) solid. Because it is often transparency and translucency, transparent and chemically inert, glass has found widespread practical, technological, and decorative use in window pane ...

. In late 2001, two important

conviction In law, a conviction is the determination by a court of law that a defendant is Guilty (law), guilty of a crime. A conviction may follow a guilty plea that is accepted by the court, a jury trial in which a verdict of guilty is delivered, or a ...

s including possession of ninja rocks were

appeal In law, an appeal is the process in which Legal case, cases are reviewed by a higher authority, where parties request a formal change to an official decision. Appeals function both as a process for error correction as well as a process of cla ...

ed. In ''People v. Gordon'' (2001) 90 Cal.App.4th 1409 (Review denied), Division 1 (

San Diego San Diego ( , ) is a city on the Pacific coast of Southern California, adjacent to the Mexico–United States border. With a population of over 1.4 million, it is the List of United States cities by population, eighth-most populous city in t ...

) of the Fourth District Court of Appeal found that possession of ninja rocks was not punishable under section 466 of the

penal code A criminal code or penal code is a document that compiles all, or a significant amount of, a particular jurisdiction's criminal law. Typically a criminal code will contain Crime, offences that are recognised in the jurisdiction, penalties that ...

. That court applied the ''

ejusdem generis Statutory interpretation is the process by which courts interpret and apply legislation. Some amount of interpretation is often necessary when a case involves a statute. Sometimes the words of a statute have a plain and a straightforward meani ...

'' rule of construction, deciding that ninja rocks were not enough alike the then-listed burglary tools. On the other hand, in ''In re Robert B.'' (2001) 93 Cal.App.4th 963, Division 3 ( Orange County) contradicted this interpretation of section 466 and upheld the conviction. On February 13, 2002, the latter case was granted review by the

California Supreme Court The Supreme Court of California is the highest and final court of appeals in the courts of the U.S. state of California. It is headquartered in San Francisco at the Earl Warren Building, but it regularly holds sessions in Los Angeles and Sac ...

. Two days later, the state assembly proposed in Assembly Bill 2015 to amend section 466 to include ninja rocks. The bill passed unanimously in both houses in August 2002.

Washington

One

Washington Washington most commonly refers to: * George Washington (1732–1799), the first president of the United States * Washington (state), a state in the Pacific Northwest of the United States * Washington, D.C., the capital of the United States ** A ...

trial court A trial court or court of first instance is a court having original jurisdiction, in which trials take place. Appeals from the decisions of trial courts are usually heard by higher courts with the power of appellate review (appellate courts). ...

found that the ability of ninja rocks to quietly break

tempered glass Tempered or toughened glass is a type of safety glass processed by controlled heat treatment, thermal or chemical treatments to increase its strength compared with normal glass. Tempering puts the outer surfaces into Compression (physics), comp ...

meant that their possession could be used to establish

intent An intention is a mental state in which a person commits themselves to a course of action. Having the plan to visit the zoo tomorrow is an example of an intention. The action plan is the ''content'' of the intention while the commitment is the '' ...

to commit burglary, even in a case where the ninja rocks were not actually thrown at any glass because the burglars had found an unlocked door. One defendant appealed his conviction to the Court of Appeals on the grounds that "the trial court erred by admitting an unusual burglary tool into evidence". The Court of Appeals denied this reasoning and upheld the conviction.

References

;Legal * **See als
Assembly
an

committee analyses of AB 2015, amon
other records

on

FindLaw FindLaw is a business of Internet Brands that provides online legal information in the form of state laws, case law and codes, legal blogs and articles, a lawyer directory, DIY legal services and products, and other legal resources. The compa ...

*San Dieg
Legal Updates: Burglary Tools
{{DEFAULTSORT:Ninja Rocks Motor vehicle theft Ceramic materials Crime in California