Catching Criminals - On Camera
Allegheny County police detectives Jim Holman and Ed Adams sometimes use a sparkly plastic rod as a prop to temper some of their colleagues'' high expectations.
"We have to pull it out every once in a while and say, ''This is a magic wand,''" Holman said.
"This," he then says, jabbing his thumb toward a wall of computer processors, monitors and other gadgets, "is not a magic wand. There''s a lot we can do with video and digital images, but there are still limitations."
They can''t pull a rabbit from a hat, but these Allegheny County police detectives are getting more calls to their 3-year-old audio/video forensics lab from investigators who want to know: "Who''s this guy on the tape?"
Images from surveillance tapes are playing big roles in some high-profile investigations.
Last month, a security camera outside a car wash in Sarasota, Fla., taped the abduction of 11-year-old Carlie Brucia, who was sexually assaulted and killed. A call from a woman who recognized the abductor from the broadcast tape led to the arrest of Joseph P. Smith, 37.
In January, Allegheny County police were able to clean up images on a surveillance video from a Penn Hills grocery store that showed Mellon Bank administrator Daniel Lynch leaving the store minutes before he was abducted and killed.
Last March 18, a surveillance camera outside a Downtown job center recorded an unknown man fatally beating, stomping and strangling Eva Haniak, 79, who often slept on the street.
The cases highlight both what police now can do with video evidence and the limitations they still face.
County police began buying the equipment in 2000 through a $250,000 grant from the National Institute of Justice.
One machine represents the first step in any forensic analysis. Tapes and discs are copied and digitized so the original recordings can be held as evidence and not damaged by the analyses.
Most store surveillance tapes - such as the one that showed Lynch leaving the grocery store - are put through a "de-multiplexer." On security systems, several cameras feed video to one tape, leaving a "multiplexed" image. One second of tape contains 60 different frames of images from as many as a dozen different cameras. Play that tape in a regular VCR, and the human eye sees just a quick blur of images.
Once the images from each camera are broken out and the speed is adjusted, another computer can take video that jumps around -- think of the tapes from cameras mounted in police cars - and stabilize the image of a particular object, such as a license plate or a gunman''s face.
The detectives have other tools to adjust the brightness and contrast of an image, and reveal objects in the darkness.
Finally, Holman and Adams can try to tackle the most-requested task: Zoom in on a face or other feature.
"That''s the one thing we often can''t do," Adams said.
In the Haniak case, Pittsburgh police sent the video to Massachusetts-based Avid Technology Inc. hoping to get a clear picture of her killer''s face. The company was able to sharpen the dark, grainy image, but only so much, city police crime unit Sgt. Paul McComb said.
"Frustrating isn''t the word," McComb said. "You can see some facial features, his shoes, his distinct clothing, but it''s just not enough."
In Sarasota, investigators who sought Brucia''s abductor reportedly asked NASA to use its video image stabilization and registration program to zoom in on the face of the man in the video and the name emblazoned on his shirt.
Adams and Holman said even NASA probably didn''t have much luck, though, because when digital video is enlarged, you just get big pixels.
"A lot of businesses are moving to digital because you can store a year''s worth of tapes on one DVD," Adams said. "But the fact is videotape is more reliable in that regard."
Most of the cases Holman and Adams investigate are convenience store robberies and burglaries, and local police have made several arrests based on the detectives'' work. They expect demand for their services to increase in coming months.
Pittsburgh police are sending cases their way, mostly because the city can''t afford to expand the small computer system in McComb''s unit. Holman and Adams also plan to hold open houses in April for municipal departments to show local officers what they can do.