If he felt insulted, Thomas didn’t show it. “This is a turnkey system called dTective,” he said, “from a company called Ocean Systems. They start with an Avid video editing system-the thing most TV shows are cut together on-and they develop hardware and software tools to customize it for forensic work. They’ve sold well over a thousand of these to police departments all over North America, including KPD, here in Knoxville. Most of those are desktop or rack-mounted systems. They call this version the ‘Luggable’; I call it the ‘Hernia-Maker.’” So he had a sense of humor. I liked that.
Chloe appeared in the doorway and ushered in a uniformed officer who was carry ing a videotape case in one hand. Thomas reached out a hand for the tape case; the officer frowned, then handed it over grudgingly.
Thomas opened the case and studied it. “And this is the original tape, right?”
“Right,” said Burt, as if the police officer weren’t even there. “You wouldn’t believe how hard I had to fight to get this. The DA’s office and KDP insisted you could work with a copy. I told them the original was the best evidence, and reminded them we’re legally entitled to the best evidence.”
He nodded. “Absolutely,” he said. “I’ll show you why in a minute.” He clicked the computer’s mouse, and the screen lit up. I had expected it to show a TV-like image from the UT surveillance camera, but instead it was a normal Windows screen, just like on my computer, except that it had a lot more program icons on it than my machine’s handful, and most of these looked unfamiliar. He clicked on one of the icons, and the screen filled with several horizontal bands, and a pair of dark circles that looked a bit like maps of the night sky, and a rectangle several inches square. He reached out a hand and Burt gave him the tape case, which he flipped open. He looked at one edge of the tape and frowned, then used a thumbnail to pry out a small tab of black plastic.
“Hey,” barked the officer, “what the fuck are you doing?”
“That’s the RECORD tab,” Thomas said. “If you want to make sure the tape doesn’t accidentally get erased or recorded over, you have to remove that tab. Your video guy should have done that the moment he got the tape.” He popped the tape into the machine, then hit PLAY. The small rectangle on his screen turned blue, with numerals, just like my television at home did when I put a tape into the VCR. Then the images began, a series of seemingly unrelated images, each on-screen for a fraction of a second, like a visual burst of machine-gun fire. After a few seconds, though, I detected a pattern. The images cycled past in a regular sequence, which I gradually recognized as hospital entrances, parking garages, and-the one that most caught my eye-the Body Farm’s gate. It was as if the pages of a dozen different books had been shuffled together at the book bindery, and to follow one story, you’d have to read one page, then flip forward ten or twelve pages to pick up the thread again. Suddenly my truck flashed past a couple of times, and I lunged toward the VCR’s controls to hit PAUSE. Thomas reached over and batted away my hand.
“Don’t touch that,” he snapped. “Do not touch that.” The officer grabbed my arm and pulled me back several feet.
“I just wanted to pause it on the truck,” I said.
“Do not touch the controls,” Thomas said. “Every time you start or stop or pause a tape, you damage it. Do it enough times, all you’re left with is snow.” He glanced in Burt’s direction. “This is one reason I hate having clients in the room,” he said. “It always complicates things.”
“I’m sorry,” I said. “It won’t happen again. Promise. I just didn’t know.”
“Okay,” he said grudgingly, then-less grudgingly-“Okay, but you’re on probation.” It sounded like maybe I wouldn’t get kicked out after all.
“Well,” I said, “that sure beats death row.”
He snorted, and Burt laughed; the cop frowned. “We’ll look at everything a frame at a time in a minute,” Thomas said. “This pass, I’m just reviewing the tape, and optimizing the levels. Then we’ll digitize it-load it into the computer’s hard drive-and once we’ve done that, we can pause, or stop and start, as many times as we want without hurting anything. Okay?”
“Okay,” I said. “I am sorry.”
“If it makes you feel any better, cops make that mistake all the time,” he said with an apologetic glance at the officer. “They get to the spot on a tape where an incident occurs-a convenience store shooting or a bank robbery-and they stop and start and rewind and slo-mo, and by the time the case comes to trial, the tape’s useless. I make two passes, three at the most, without ever stopping the tape anywhere in the event sequence.”
As he talked and the images strobed by, he slid and clicked the mouse rapidly, and the computer’s cursor flitted from one pull-down menu to another. As it did, I noticed slight changes in some of the images flickering past-dark images got brighter, washed-out images got toned down, and some colors seemed to fade while details got crisper in shades of gray. After a few minutes, the dark, nighttime shots gave way to sunlit images, and I noticed police vehicles and uniformed cops at the Body Farm. Thomas looked at Burt and asked, “We’re past the event sequence now?” Burt nodded. Thomas hit STOP and rewound the tape to the beginning, then hit PLAY again.
“How are we going to tell anything meaningful from that jumble of images?” I asked as they flashed past again. “It looks like they wired a whole bunch of cameras to one VCR.”
“That’s exactly what they did,” he said. “It’s called multiplexing. Saves a lot of money on recording decks and tape. In an ideal world, you’d have a separate tape for each camera, recording in real time, and you’d archive all the tapes. But if you did, you’d end up with seventy thousand tapes a year.”
“That’s a lot of tapes,” I conceded.
“A video camera records at thirty frames a second, and it looks like they have sixteen cameras, so in this setup, each camera grabs one frame of video about every half second. Not a bad compromise.”
“But everything’s all jumbled up,” I said.
“Patience, my friend,” he said. “There’s a tool in dTective called ‘Deplex’ that demultiplexes the feeds-separates them, like unraveling a rope into individual strands-so we can play the video from one camera at a time.”
After he’d recorded the entire nighttime sequence, he stopped and rewound the tape once more, then ejected it, tucked it back into its case, and handed it to the police officer. “Okay, we’re done,” he said. “Thanks very much.” The officer nodded; he hesitated, almost as if hoping to be asked to stay, then turned and left.
“You’re done?” I asked. “But we haven’t looked at anything yet.”
“I just meant I’m through digitizing the original,” Thomas said. “Now we’ll work with this digital copy. And if something terrible happens as we’re working with it, all we lose is a copy, not the original.”
“How come UT’s still recording on videotape,” I asked, “given that even home video cameras are starting to record on memory cards and hard drives?”
“Storage space and data quality,” he said. “One hour of images from these cameras would require seventy-two gigabytes of storage. Multiply that times twenty-four hours in a day, times thirty days in a month, and pretty soon you’d need a supercomputer to store it all. You can save space by compressing the images, but when you compress, you lose a lot of the details. To use a nontechnical analogy, the image quality goes from being more like a glossy photographic print to being more like a newspaper photo, which turns into a grainy collection of dots if you look at it closely. More and more surveillance systems are going to digital,” he acknowledged, “but nearly all the big Las Vegas casinos-which spend millions on security-still think tape is better.” He did more clicking, and sixteen postage-stamp-sized images came up on the monitor. “Okay, there are the sixteen camera angles, separated by the deplexer. Looks like it’s camera nine that we’re interested in.” He clicked on the thumbnail showing the Body Farm’s gate, illuminated by the streetlights in the parking lot, and that image enlarged until it filled about half the screen.