The International Defensive Pistol Association (IDPA), founded in 1996, is an organization based in Bogata, Texas, that has created a shooting sport based on defensive pistol techniques, using equipment including full-charge service ammunition to solve simulated "real world" self-defense scenarios. Shooters competing in defensive pistol events are required to use practical handguns and holsters that are deemed suitable for self-defense use and concealment garment that can conceal the handgun from view of bystanders.
The sport came about as a response to the perceived shortcomings in competitions organized by the United States Practical Shooting Association (USPSA) and its migration away from the use of common, un-customized handguns. It was decided by the founders of IDPA (Bill Wilson, John Sayle, Ken Hackathorn, Dick Thomas, Walt Rauch and Larry Vickers), that USPSA competitions had become too far removed from the reality of defensive shooting situations, using extensively modified guns, handmade ammunition, and speed-draw holsters that were impractical for self-defense. The IDPA founders believed that USPSA matches had become "equipment races", which were heavily dependent on a shooter's gear rather than their ability.
In order to keep the sport in line with its founding principles, allowable alterations to the competition gear (including pistol or pistol caliber carbine) are carefully regulated in IDPA. Ammunition capacity is limited compared to some other action shooting sports in order to keep the playing field level for competitors from states that ban higher capacity magazines.
Scoring
Scoring at each match is based on the time taken to shoot the stage plus time added for any penalties accrued. Penalties are given for poor marksmanship (i.e. posting hits outside the targets' highest scoring area), failure to use cover, failure to follow a Safety Officer's directions, or any violation of IDPA rules. Penalties range from one second per dropped point on targets up to 20 seconds for a Failure to Do Right which is a blatant violation of IDPA rules—i.e. cheating or unsportsmanlike conduct.
Unlimited Scoring
Most IDPA stages are scored using Unlimited Scoring (previously known as Vickers Count) which means that shooters may fire as many rounds as they feel necessary to make the specified number of hits. The best hits on the target are the only ones that count for score. If a stage calls for two hits on each target, a shooter may fire as many rounds as desired and no penalty will be given. Only the best two hits will count.
Limited Scoring
On a standards stage (an exercise intended to test marksmanship and gun handling skill as opposed to being a scenario) it is common for the course of fire to specify Limited scoring (previously known as Limited-Vickers). On this type of stage, the shooter may fire no more than the number of rounds specified. Firing more rounds will earn a procedural penalty and only the lowest scoring hits on target, of the number specified in the course of fire, are counted. For example: a Limited Scoring stage calls for two shots fired; the shooter fires one round into the -0 zone and one round into the -1 zone; if they fire again, hitting the -0 zone; when the target is scored, only the -0 and -1 zone hits will count. The "make up" -0 shot will be thrown out (not because it is the make up, but because is a higher score and the rationale is there should be no possible advantage accrued from failing to follow the stage procedure) and the shooter will be assessed a procedural penalty for firing more shots than the course called for. In addition, the shooter will have also added to their score by taking the time to fire the extra round.
Points Down
Originally the IDPA target was marked with two 5-point zones (head and circle in center), a 4-point zone (a polygonal box around the circle), and a 2-point zone (the outside periphery of the target). However, since scoring is obtained not by calculating points obtained but by subtracting points dropped, the scoring zones came to reflect that system.
The current standard IDPA target is a cardboard humanoid shape with scoring zones perforated onto its surface. There are two areas marked as "-0" or "down zero" (the head and center-mass of the body represented by a circle, which has been moved up from its original position to be higher in the target body, thus more closely approximating the location of the heart and surrounding arteries) and two marked "-1" (the area outside the -0 in the head and in the body) and one marked"-3".