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Law Enforcement
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The dangers of digital
In-car camera systems face potential scrutiny
Mar 4, 2005
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by staff
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In-car video recording has become a vital tool for police departments, prosecutors, and reality TV shows. While the public and police are now accustomed to being on “Candid Camera,” serious questions are being raised about the admissibility of in-car digital video in court.
The reason: Unlike analog video, there are no standards that govern the minimum quality and resolution of digital video images. Without such standards, in-car digital video users can’t be sure that the quality of compressed video they are shooting will stand up in court, said Grant Fredericks, a forensic video analyst and former police officer who now heads up Avid Technology’s forensic video division.
“The problem is the amount of video compression being applied to the footage in order to maximize storage on the patrol car’s hard disk,” Fredericks told Government Video. “If too much information has been stripped from the image during compression — and too many artifacts occur when it is reassembled during playback — the defense can argue that the footage isn’t sufficiently reliable.
“If the prosecutor can’t convince the judge otherwise, the digital video could get thrown out of court. In turn, any subsequent video shot at the same or higher compression rates could also be inadmissible, rendering the local police department’s in-car digital video investment worthless.”
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| The Gemini digital in-car video system from Decatur Electronics includes a 4.75-inch touch screen, digital video recorder, and a Sony camera. |
While courtroom evidence is certainly a concern, “about 90 percent of the bad guys plead out and the video never has to enter a courtroom,” said Larry Sharp, director of engineering for International Police Technologies, which produces video evidence systems. “Presently, the key to utilizing digital video in the in-car police application is finding the right balance of quality of reproduced images to usefulness ... to budget. Unfortunately, simply dictating a set frame resolution, frame rate, and compression methodology or standard doesn’t entirely solve the problem, either. There are a range of internal codec settings that dictate quality as much as these ‘large’ parameters.”
The Good News
Despite the problems caused by too much compression, digital video does offer substantial advantages for in-car police systems (or any kind of surveillance video). For example, many digital video systems come with a video looping buffer, a RAM or hard disk cache that automatically retains the last 30-60 seconds seen by the car’s front-mounted video camera. When a patrol officer triggers his lights, whatever situation convinced the officer to act is automatically transferred from the buffer to the hard disk. In contrast, a patrol car equipped with a light-activated VCR will miss the incident, because it doesn’t have this feature.
In Texas, after replacing 60 in-car analog video systems with digital systems, the Tyler Police Department has become a big advocate of video looping buffers (see Government Video, September 2004). “The video looping feature means that we typically capture incidents from start to finish,” explained Sgt. John Bausell, TPD technology coordinator. “For instance, when an officer witnesses an erratic driver on the road, the driving that caught their attention is part of the public record. This makes it much easier to get convictions, because the evidence of the incident is indisputable.”
In addition, when compared to analog videotape, digital video is much easier to store, access, and retrieve. Digital video is recorded on portable hard disks, which are then downloaded into a police department server at the end of shift. Whenever digital video footage is needed, a good asset management system makes searching relatively easy. And making copies is as easy as copying a text file.
In contrast, videotapes are a hassle to copy and a bigger hassle to search. Other issues include cataloging and the space issues associated with physically storing the tapes.
The Bad News
While compression has already been discussed, another issue with digital video that bears mentioning is forensic image analysis. Anyone who watches CSI has seen Hollywood’s version of forensic video technology: A grainy surveillance video is replayed on a crime lab computer where, after a few clicks, a close-up of a victim’s fuzzy eye suddenly gains enough resolution and clarity to reveal the face of his attacker.
In real life, of course, forensic video analysis is neither this easy nor precise. “There is an analog video enhancement technique called time frame averaging that can turn a blurry license plate into a crystal clear image,” offered Grady Baker, project director of the IACP’s in-car video survey. However, digital video can’t be enhanced, because images are built using tiny pixels. Enlarge the image and you enlarge the pixels — not even CSI can change that.
Unfortunately, because of the popularity of CSI and its two spin-offs, the public has accepted TV’s fanciful version of image enhancement as fact. This has resulted in what Fredericks called “the CSI factor,” where juries acquit defendants because the police video isn’t up to the quality that the jurors believe it should (or could) be. “The acquittals occurred because the juries thought the police were holding something back by not offering higher video resolution, which of course they weren’t,” Fredericks noted.
There are also questions about the admissibility of digital video in court. With analog video, you could subpoena the original tape, but does the defense subpoena the hard drive? Not possible — remember, the video gets transferred from the patrol car’s hard drive into the department server at the end of shift, then the drive is wiped and used again.
Still, there are watermarking and other procedures that can keep the chain of evidence from breaking. Some manufacturers provide an alternative digital storage solution. “The idea of recording digital video files and keeping the original is possible with the DVD-RAM format that we offer,” explained Dave Teeter, product manager for Kustom Signals. “We, of course, also offer a system that records to hard drives, but we have many agencies that are concerned about the original recording issue or about the cost of a large server, and are managing RAM discs like they have managed VHS tapes.”
Realistic Standards
If digital video doesn’t offer the standards and enhancement capabilities offered by analog video, should police departments should stick with analog? The answer is a matter of opinion, but as Fredericks pointed out, analog video is on its way out no matter what anyone thinks. The IACP’s Grady Baker agreed: “There’s actually nothing wrong with analog video, it’s just the technology of the past.”
The real issue is not whether to resist the digital revolution, but how to join it without compromising too much on quality. “After all, it’s possible to build digital video systems that are superior to analog, but their cost would be prohibitive,” Baker said. “The key is to buy digital video systems that provide legally acceptable quality and compression at an affordable price.”
But what exactly constitutes “legally acceptable” video quality? This is a question that the FBI’s Scientific Working Group on Imaging Technology has been trying to answer. In a February 2004 document, “Recommendations and Guidelines For The Use Of CCTV Security Systems For Commercial Institutions,” SWGIT recommended that DVRs record each frame at a minimum resolution of 640x480 progressive or 640x240 interlace (and at least one field recorded every second). As for compression, SWGIT recommended that the “lowest possible amount of compressed be used in recording files.” Lossless (no data lost) compression is best, as opposed to lossy compression, which reduces file sizes by discarding data that isn’t considered critical (and that could cause problems during analysis).
“My thoughts as to the proper way to set a quality ‘standard’ would be a process of driving a digital-video-system-equipped vehicle over a set course with minimal standards regarding acceptable video quality, such the ability to distinguish text or other reasonable expectations,” Sharp said. “The majority of video is of the back of a car with the officer standing next to the offending driver. Agencies will have to accept that their cost of meeting this ‘standard’ may be the increased cost of video storage and longer upload times. Agencies faced with long court-mandated storage times will especially be hit by trying to meet this empirical standard.”
Fortunately for in-car video users, some systems suppliers do offer video storage options that apparently comply with SWGIT’s recommendations. Kustom Signals, for example, offers a 720x480 video storage solution that records at 30 fps. Greg Direnzoes, manager of Decatur Electronics, said his company can support various compression and frame rates requested by customers.
As to whether current digital video systems will record legally admissible video, even with the guidance of SWGIT’s recommendations, this is still a “buyer beware” situation, according to Fredericks. “Ask vendors for white papers that detail how their products have been tested, and against what standards,” he suggested. “Walk away from anyone who says their system has been certified as providing legally admissible video, because no such certification exists.”
Also, talk to local prosecutors and anyone who may be using your video in court. Once you have their input, you’ll be in a better position to set quality and compression standards for digital video vendors, rather than letting them set standards for you.
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