Pit bulls are a breed of bull terrier. They were bred largely for fighting purposes, and thus tend to have a highly aggressive attitude that can make them a serious danger, especially to children.
Pit bulls have become a focus of media and legislative attention, with some groups alleging that they should be considered dangerous weapons, and banned (as in the U.S. city of Denver), and some defending them by claiming that individual pit bulls are just as variable as any other breed.
The issue of pit bulls and their purported danger to society has been hotly debated in recent years. There are two opposing sides: One says that pit bulls are no more dangerous than any other breed of dog, as their behavior is influenced more by their training than heredity and that they should not be discriminated against or treated differently, while the other side maintains that pit bulls pose a real danger to society due to their aggressive nature, propensity to unprovoked attacks, and great physical strength.
The relatively low incidence of serious attacks by dogs makes it difficult to accurately assess any claims about the dangers pit bulls might present. While it does seem to be true that pit bulls are over-represented among attacks that led to serious injuries and fatalities, the very low numbers make it difficult to come to any conclusions. This is especially true when one considers that any dog owner who intends to train a dog to fight, thereby making it much more dangerous to others, is very likely to pick a pit bull. In this way, the proverbial danger of a pit bull verges into a self-fulfilling prophecy.
Taking the above with a huge grain of salt is highly recommended, as Dogsbite.org is highly unscientific. However, for those of you interested in actual studies from proper science here is what the Journal of Forensic Science has to say: The owners of vicious dogs, regardless of the breed, had “significantly more criminal behaviors than other dog owners.” They go on to conclude that “vicious dog owners were higher in sensation seeking and primary psychopathy,” and further concluded that “vicious dog ownership may be a simple marker of broader social deviance.”
One of the most problematic aspects of the debate over pit bulls is the question of identifying them. It is generally agreed that "pit bull" refers to one of a variety of breeds of bull terrier, most commonly the Staffordshire bull terrier and the American bull terrier. But as with all breeds, only a relatively small fraction of dogs are purebred, i.e. 100% "pit bull." Instead, many are mixed breeds. This makes it difficult to even decide on what a pit bull is, even before the difficult question of their possible management.
It is indisputable fact that both breeds of dog were bred for fighting. They are "pound for pound, one of the most powerful breeds of dog ever developed," and have a "very high pain threshold." But the breeds' suitability for fighting does not mean that each animal is inherently a fighting dog, and opinion is mixed on what degree of danger is inherent in having some quantity of pit bull blood.
Although owners of pit bulls often term their dog an "American Pit Bull Terrier", the AKC (American Kennel Club) does not list the American Pit Bull Terrier (or "Pit Bull") as an AKC registered breed or consider it a "purebred" dog,  so there are no exact standards by which to characterize any individual dog as a "pit bull."
However, many states have enacted "breed-specific" laws that contain language that defines what they consider legally to be a pit bull. Michigan describes a pit bull as:
- American Pit Bull Terrier,
- American Staffordshire Terrier,
- Staffordshire Bull Terrier or
- any dog displaying or exhibiting the distinguishing characteristics or a majority of physical traits of these breeds.
Cabot, Arkansas  uses the above language, but widens the description to add:
- Dogs of mixed breed containing one of the aforementioned breeds
- Any dog that has the appearance and characteristics of the aforementioned breeds
Pit bulls in the United States
Terriers were bred to be working dogs: sheep herders, rat attackers, etc. pit bulls emerged as people bred these dogs to be more aggressive and physically tough.
The name "pit bull" comes from their original intended purpose: two dog owners would dig a pit in the ground, then throw in their dogs to fight to the death. The pit would ensure that the dogs could not leave, and would have to continue to fight until one fatally wounded the other.
Dog Fighting in the United States
Dog fighting initially had little to no restrictive laws, but as the conditions of dog fighting became more widely known, and people realized the violence of the "sport" and the pain and destruction caused to the dogs, there arose a sentiment that causing dogs to fight was cruel. Animal protection laws began to be proposed and passed at an ever increasing rate,When? and included other animals that were made to fight, such as birds.
Advocates of dog fighting compared it to fighting sports such as boxing. Those opposed to dog fighting maintained it was not the same, as human beings are free to choose to fight or not, while the dogs did not have a choice, and were forced to fight. A boxer can also choose to give up, and the fight ends if a boxer is knocked out, while pit bulls were forced to fight to the death.
Studies of pit bull attacks
Although pit bull fighting is against the law in the United States, illegal fights are still held, and the dogs' presence is still high. Problems occur when the dog owners who own Pit Bulls as pets lose control over them, and the dogs attack people. As more and more incidents involving pit bulls have been reported, agencies and organizations began investigating the involvement of pit bulls in dog bites/attacks.
An early AVMA (American Veterinary Medical Association)  study titled "Breeds of dogs involved in fatal human attacks in the United States between 1979 and 1998"  found that "Pitt Bull type and Rottweiler dogs were responsible for more than half the deaths reported from dog attacks", and that "fatal attacks on humans appear to be a breed-specific problem", yet at that time they did not advocate "breed-specific" regulations.
A 2000 study and report by the Center for Disease Control (CDC) that compiled statistics on attacks and deaths caused by various dog breeds concluded that pit bulls should be considered a danger to public safety and recommended enacting "breed-specific legislation" and regulations of "dogs and owners on the basis of behavior". 
The American Veterinary Medicine Association has found via proper science: "controlled studies have not identified this breed group as disproportionately dangerous." 
Contrary to popular opinion, a bite from a Pit Bull is not worse than from other dogs. In fact, bite force coorelates to body weight , the American Pit Bull Terrior thus has less bite force than Rotweillers and German Shepards (both larger dogs.)  There is absolutely no truth to the claim Pit Bulls have a locking jaw.
The National Canine Research Council states that "study of dog bite-related fatalities occurring over the past five decades has identified the poor ownership/management practices involved in the overwhelming majority of these incidents: owners obtaining dogs, and maintaining them as resident dogs outside of regular, positive human interaction, often for negative functions (i.e. guarding/protection, fighting, intimidation/status); owners failing to humanely contain, control and maintain their dogs (chained dogs, loose roaming dogs, cases of abuse/neglect); owners failing to knowledgably supervise interaction between children and dogs; and owners failing to spay or neuter dogs not used for competition, show, or in a responsible breeding program." And unlike the screaming lunacy claiming that Pit Bulls are inheriantly dangerous, this study includes methodology. 
Laws specific to pit bulls
Since then, many states have termed Pit Bulls a dangerous breed of dog and have enacted laws pertaining to how they are housed and the extent and manner in which they can interact with the public.
These laws commonly require such measures as:
- higher registration fees
- mandatory spaying/neutering
- bans on ownership, sale, and breeding of Pit Bulls
- dogs directed to be kept in secure, locked enclosures, with posted warning signs
- public leashing and muzzling
- microchipping and/or tattooing
- owners are required to carry liability insurance
The laws mandate penalties for violations, usually monetary fees or fines, but in some cases include jail time.
Some examples of state legislation:
- Florida: in Miami-Dade County, it is illegal to own a pit bull; violations carry a $500 fine.
- Massachusetts: in Boston,  Pit bulls must be muzzled in public, violations carry a $100 fine. 
- Ohio: Mahoning County requires pit bulls to be kept in a locked pen or enclosed yard and be leashed and muzzled in public. Owner must also carry liability insurance of $100,000 per dog.  and in the city of Akron, Ohio, in addition to the insurance requirement, owners must also post a city issued warning sign, provide two photos of their dog, tattoo or microchip the animal, and the dog must wear a fluorescent Green dog collar. 
- Maryland: Prince George County Code, Section 3-185.01, states: "No person shall own, keep, or harbor a Pit Bull Terrier within the County." Fines can be up to $1,000 or up to six months of imprisonment. 
- Texas: the City of Garland requires that pit bulls be kept contained inside a six foot tall fence, made of wooden planks at least ½ inch thick or 11 gage chain link fencing, with no gaps or openings larger than 2 inches. All gates must have a locking mechanism that keeps the gates securely closed. 
- Delaware: the City of Wilmington mandates that Pit Bull owners must be at least 21 years old. Pit bulls must be neutered, and breeding them is prohibited. The dogs must be leashed and muzzled in public. Fines are $500 first violation, $1000 for repeat violations. 
- Kansas: the City of Salina maintains a public map of registered Pit Bull owners home address or other location of the dogs  and dogs must be: registered, muzzled, kept in specific types of enclosures which are equipped with warning signs, photographed, microchipped, have a special permit and special collar when in public, and cannot be sold or given to anyone except under specific limited circumstances. 
- Arkansas: the City of Little Rock passed laws in 2004 (Ordinance 7673) banning pit bulls from being brought within the city limits. Dogs already residing within city limits are required to be: spayed/neutered, assigned a control number, tatooed with the control number, kept in a secured building or outside area equipped with a lock and posted warning signs. 
- Georgia: State legislature enacted in 2005 states "It shall be unlawful for any person to import, sell, transport, carry, own, keep, or otherwise possess any live pit bull within the state".  Pit bulls owned prior to enactment of the law must be neutered, confined, leashed & muzzled in public. The law states that "Any person found guilty of violating any provision of this Code section shall be guilty of a misdemeanor and shall be fined not less than $1,000.00 nor more than $5,000.00 or incarcerated for a period not to exceed six months, or both".
- Missouri: Springfield City Council Bill No. 2006-113 requires many of the same restrictions as the earlier enacted laws of other states: pit bulls must be registered, spayed, microchipped, kept in secure enclosed areas, and muzzled while in public. 
- Kentucky: the City of Covington defines pit bulls as vicious dogs and requires them to be spayed/neutered, photographed, microchipped, leashed and muzzled in public, and requires owners to maintain insurance of $100,000. 
It should be noted that all of the above fails to take into account the wild variations within how each area defines "Pit Bull" and the Journal of Applied Animal Welfare Science found that “87.5% of the dogs identified by an adoption agency as having specific breeds in their ancestry did not have all of those breeds detected by DNA analysis.” 
There have been cases where dog owners questioned or challenged the right of the government to make laws regarding pit bulls. States maintain that it is their right, both legally and in the interest of public safety.
- Utah, South Jordan: enacted a ban on pit bulls (Ordinance 7.12.125 - South Jordan City Municipal Code) and declared it to be: unlawful to own or harbor a Pit Bull or any breed that strongly resembled the physical traits of an American Pit Bull Terrier, American Staffordshire Terrier, or Staffordshire Bull Terrier within the city limits of South Jordan City. The law further states: "In 1997, the City Council determined the Pit Bull breed to be dangerous after hearing testimonies regarding attacks by the Pit Bull. The City Council found that the breed possess extremely powerful jaws, high pain tolerance, extreme aggressiveness towards other animals, they have a natural tendancy to refuse to terminate an attack once it has begun. The City Council found that these traits result in significantly greater damage to persons and property than attacks by other canine breeds. The purpose of this ordinance is to ensure the protection of the public health, safety and welfare." 
- The Municipal Code of Toledo, Ohio includes language that says: "The State of Ohio and City of Toledo have a legitimate interest in protecting citizens from the dangers associated with Pit Bulls. Toledo's Municipal Codes are rationally related to the government's interest and are constitutional." 
- Albuquerque, New Mexico, keeps a list of dogs termed "dangerous", and Chapter 9, Article 17, of their City Ordinance, known as "Angel's Law" reads: "This ordinance was established to protect the public, especially young chidren and others unable to protect themselves from vicious attacks, and the threat to health and safety that dangerous dogs present." 
This language is similar in many of the laws that have been enacted against Pit Bulls.
Pit bull studies in Canada
In 1990, Winnipeg was the first major Canadian jurisdiction among several to ban pit bull-type dogs. In 2005 Ontario adopted a province-wide ban on pit bulls. Edmonton requires that vicious dogs be muzzled in public and that the American Staffordshire terrier and Staffordshire bull terrier (breeds often included under pit bull-types) be automatically considered vicious.
A 2008 study published by Canada's Health Institute on fatal dog attacks between 1990-2007 identified 28 fatalities from dog bites. 
An April 2011 Canadian dog bite study was conducted by physicians and consisted of a review of 82 cases at a level 1 trauma center. Where the breed of dog was identified, the researchers concluded that attacks by pit bulls are associated with higher morbidity rates, higher hospital charges, and a higher risk of death than are attacks by other breeds of dogs. 
A recently published report by DogBite.org that reported statistics on US and Canada dog bite injuries and deaths from 1982 - 2011 found that: The combination of pit bulls, rottweilers, their close mixes and wolf hybrids caused:
- 77% of attacks that induce bodily harm
- 73% of attacks to children
- 81% of attack to adults
- 68% of attacks that result in fatalities
- 76% that result in maiming
and states that: "Even if the pit bull category was split three ways, attacks by pit bulls and their closest relatives would still outnumber attacks by any other breed. Pit bulls are noteworthy for attacking adults almost as frequently as children, a characteristic not shared by any other breed. If a pit bull or rottweiler has a bad moment, instead of being bitten, often someone is maimed or killed; that has now created off-the-chart actuarial risk." 
The Rest of the World
Pit Bulls are banned under the Dangerous Dogs Act
Australia has a number of laws depending on which state you're in 
Pit bull temperment
As the above scare mongering has likely caused some concern, according to the American Temperament Test Society, a group that performs testing that documents their methods  The American Pit Bull Terrier and the American Staffordshire Terrier rank in the top 80% for aggreable temperment.  The average passing rate for the other 121 breeds of dogs in the tests: 77%.
Of course, no Chihuahua is all that dangerous, regardless of how angry and ill-tempered it is, unless you count nipped ankles among your casualty counts.
The recent moral panic over the dangers of Pit Bulls is not the first time a specific breed of dog has been targetted as supposedly "vicious." In fact, your average droopy faced Bloodhound was once considered a fearsome slayer of men and housecats. 
A study conducted by the National Canine Research Council in 2008 concluded there was significant media bias in the reporting of Pit Bull related dog attacks over attacks by other breeds.  Of specific interest was a woman fatalled mauled by Labradors which was not picked up by anything more than local news, while that same year a similar attack by a pitbull "was covered by at least 285 media outlets, both nationally (in 47 U.S. states) and internationally (in eight other countries). MSNBC, Forbes, USA Today, Fox News, CBS News, and ABC News all picked up the story.”
- ↑ Excerpt of relevant city code
- ↑ 2011 U.S. Dog Bite Fatality Statistics, Dogsbite.org. Statistics may be skewed, as they are collected by an anti-pit bull advocacy group.
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/19302402
- ↑ Fiedler, Julie. Pit Bulls. New York: Rosen Publishing, 2006
- ↑ Stahlkuppe, Joe. American Pit Bull Terriers/American Staffordshire Terriers. New York: Barrons.
- ↑ http://www.akc.org/breeds/breeds_h.cfm
- ↑ http://www.legislature.mi.gov/documents/2011-2012/billintroduced/House/htm/2011-HIB-4714.htm
- ↑ http://www.cabotar.gov/department/division.asp?fDD=13-133
- ↑ http://www.aspca.org/fight-animal-cruelty/dog-fighting/dog-fighting-faq.aspx
- ↑ http://animallaw.info/articles/ovusstatedogfightingchart.htm
- ↑ http://www.avma.org/
- ↑ http://www.avma.org/avmacollections/canine_behavior/javma_217_6_836.pdf
- ↑ http://www.cdc.gov/HomeandRecreationalSafety/images/dogbreeds-a.pdf
- ↑ https://www.avma.org/KB/Resources/Backgrounders/Pages/The-Role-of-Breed-in-Dog-Bite-Risk-and-Prevention.aspx
- ↑ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2423399/
- ↑ http://dogfacts.wordpress.com/2008/02/03/national-geographics-dr-brady-barrs-bite-pressure-tests/
- ↑ https://en.wikipedia.org/wiki/Pit_bull#Locking_jaws_myth
- ↑ http://nationalcanineresearchcouncil.com/uploaded_files/tinymce/Delise%20Research%20&%20Investigation%20Methodology.pdf
- ↑ http://www.miamidade.gov/animals/pitbull-law.asp Pit Bull Law Dade County ordinance, Chapter 5, Sec. 5-17
- ↑ http://www.cityofboston.gov/animalcontrol/regulations/pitbull.asp
- ↑ http://www.cityofboston.gov/Images_Documents/pitbull_ord_tcm3-3385.pdf
- ↑ http://www.mahoningcountyoh.gov/DepartmentsAgencies/Departments/DogWarden/PitBullTerrierNotice/tabid/930/Default.aspx
- ↑ http://akronohio.gov/311/pdf/PitBullRegistration.pdf
- ↑ http://www.princegeorgescountymd.gov/Government/AgencyIndex/DER/AMG/licenses.asp
- ↑ http://www.garlandtx.gov/gov/ab/animals/pitbull.asp
- ↑ http://www.wilmingtonde.gov/residents/animals
- ↑ http://www.salina-ks.gov/content/126/198/10558/10613.aspx
- ↑ http://www.salina-ks.gov/filestorage/126/198/10558/SalinaCodeArctle9Sec7_144.pdf
- ↑ http://www.northlittlerock.ar.gov/pdfs/PitBull.pdf
- ↑ http://www1.legis.ga.gov/legis/2005_06/fulltext/hb78.htm
- ↑ http://health.springfieldmo.gov/index.aspx?NID=211
- ↑ http://www.covingtonky.gov/documents/PIT_BULL_and_VICIOUS_DOG_REQUIREMENTS.pdf
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/20183478
- ↑ http://www.sjc.utah.gov/police/police-animalcontrol-ordinances.asp
- ↑ http://www.supremecourt.ohio.gov/rod/docs/pdf/0/2007/2007-Ohio-3724.pdf
- ↑ http://www.cabq.gov/pets/dogs/dangerous-dogs
- ↑ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2387261/
- ↑ http://dogbitelaw.com/dangerous-vicious-dogs/overview.html
- ↑ http://www.dogsbite.org/dog-bite-statistics-study-dog-attacks-and-maimings-merritt-clifton.php
- ↑ http://www.legislation.gov.uk/ukpga/1991/65/contents
- ↑ http://www.ava.com.au/sites/default/files/AVA_website/pdfs/Dangerous%20dogs%20-%20a%20sensible%20solution%20FINAL.pdf
- ↑ http://atts.org/tt-test-description/
- ↑ http://atts.org/breed-statistics/statistics-page1/
- ↑ http://nationalcanineresearchcouncil.com/uploaded_files/publications/230603563_Pit%20Bull%20Placebo.pdf
- ↑ http://nationalcanineresearchcouncil.com/uploaded_files/tinymce/2008%20Media%20Bias_1.pdf