Performing the glitch
The glitch revolves around a flaw in the structure of the top floor of the Lucerne Tower (which is the name of the dataDyne skyscraper). It can be accessed by first taking a running jump (well, fall) off the helipad onto the top of the level's first door (which must first be opened outwards for this to work).
Once this is done, turn left, crouch once and move slowly forwards through the light panel to enter a glitchy kind of area from which the dark interior of the skyscraper can be seen.
From this position it is possible to swiftly speed-strafe right and exit the Lucerne Tower completely, free-falling through the level. You need to pick your direction very carefully, and uncrouch right away after you begin to move to get the speed needed to pull off the glitch properly.
A variety of positions lower in the level can be accessed extremely quickly by this method, including the secret "cheese room" (which is not actually ever used for speed runs), Cassandra de Vries' office, the room where the programmer deletes Dr. Carroll's file on Perfect Agent, an external balcony which rings the office floors (a structure which was originally going to be an integral part of the level but was abandoned), the ground floor lobby, an area of pavement outside the Lucerne Tower's front door, and, most importantly, the basement elevator. You can also fall all the way out of the level into oblivion.
For speed runs, the Defection glitch can also be pulled off by landing on the head of a patrolling guard as he walks through the door that you usually use. This is tougher, but consistently faster.
When the glitch is used
The Defection glitch is exploited in the world record strategies for Defection Agent, Special Agent and Perfect Agent. As the level is precisely identical for dataDyne Central: Extraction and Mr. Blonde's Revenge, the Defection glitch also works on these missions, but it is pointless as these levels need you to ascend the skyscraper.
Its original discovery caused a long-lasting storm in Perfect Dark circles as it enabled the world record for the first level (at the time, 33 seconds) to be lowered to its current 5 seconds, most of which the player spends free-falling directly into the basement elevator. Modifications of the technique later allowed similar improvements to the SA and PA records.
The Defection glitch has always been a handy promotional tool for The Elite, as it allows the very first level of the game, Defection Agent, to be beaten in a time which the layman would at first sight deem completely impossible (as the elevator ride alone takes longer than 5 seconds). This has the effect of stunning most newcomers who cast a casual glance over the Perfect Dark Elite's world records page.
- 0:15 ... has been accomplished! - the thread in which the glitch was first announced