The idea for the Screamer was for him to lurk in different areas, much like the Witch, paying no attention to his surroundings until coming in contact with a Survivor whereupon, if sufficiently agitated, he would run away from Survivors in an attempt to hide. If he succeeded in escaping, he emitted a loud scream that alerted ahorde, causing an attack - thus, foreshadowing the later Boomer bile concept, and additionally helping to establish early on in production that the Common Infected are driven to extreme aggression as a response to loud noises. It was therefore important for the players to kill the Screamer before he could escape and call a horde. Since the Screamer was under physical restraint, he did not have the ability to mount any direct attack on Survivors.
As stated in the Developer Commentary, Screamers and Boomers co-existed for a time during development. At the time, the Boomermerely exploded when killed, causing damage to nearby Survivors, while the Screamer would attract hordes with his scream. Ultimately, the Screamer was cut from the game because he was deemed too difficult and confusing for the Survivors to spot and track down amongst a crowd of Common Infected. However, the idea of a Special Infected having an attack that attracts a horde was considered too good to go to waste, and the Boomer was then given its bile attack and its bile splash death effect.
The Screamer serves as the progenitor for the Hunter, Witch, the retail version of the Boomer, and the Jockey, as well as the Fallen Survivor. His screams were recycled as the warning for a Hunter's pounce attack. He stood idle in place until alerted, which later was an attribute given to the Witch. His screams attracted horde attacks, like the retail Boomer's bile attack, and he cackled maniacally, like the Jockey, who is also speculated to have been insane prior to infection. And the Fallen Survivors run away from Survivors, much like the Screamer, in an attempt to escape.
The straitjacket is usually used as a restraint to prevent mental patients from harming themselves and others. Since the Screamer is bound in a straitjacket, it hints that the Screamer was formerly either a mental institution patient or an early on-set Infection victim restrained due to the disease's crazed symptoms.
The Screamer bears a resemblance to the Siren in the game Killing Floor. Both wear straitjackets and scream. It could also be viewed as resembling the Lying Figures from Silent Hill 2, who run in straitjackets made of their own flesh and spit out bile acid.
The Jockey has sounds that may have been recycled from the Screamer, as Jockeys cackle maniacally in-game, something that Screamers would have done.
Judging from concept art, the Screamer has the same shoes as the Hunter.
There are no existing screenshots or models of the Screamer other than its concept art.
The Fallen Survivor in the DLC campaign The Passing behaves like the Screamer, as he retreats from the Survivors if they attack him. He does not call for hordes to attack, however.
Although the Screamer does not have any legacy textures or models remaining in-game, his scream is still available as part of both Left 4 Dead's sound files for the Hunter. His ear-piercing scream is called "shriek_1" in the 'player/hunter/voice/attack/' directory.
In the first Left 4 Dead trailer, a scream is heard at the beginning. This was originally used as the Screamer's voice; however, it was eventually recycled for the Hunter to use when he pounces.