“That’s just about right,” she said. “Intensive care for video.” She ejected one tape, stuck in another, and started it up. “Oops. Did you say this material was original? It’s not. These tapes are copies.”

“How do you know?”

“Because we got a windup signature.” Theresa bent over the equipment, staring at the signal traces, making fine adjustments with her knobs and dials.

“I think that’s what you got, yes,” Sanders said. He turned to me. “You see, with video it’s difficult to detect a copy in the image itself. The older analog video shows some degradation in successive generations, but in a digital system like this, there is no difference at all. Each copy is literally identical to the master.”

“Then how can you say the tapes are copies?”

“Theresa isn’t looking at the picture,” Sanders said. “She’s looking at the signal. Even though we can’t detect a copy from the image, sometimes we can determine the image came from another video playback, instead of a camera.”

I shook my head. “How?”

Theresa said, “It has to do with how the signal is laid down in the first half-second of taping. If the recording video is started before the playback video, there is sometimes a slight fluctuation in the signal output as the playback machine starts up. It’s a mechanical function: the playback motors can’t get up to speed instantaneously. There are electronic circuits in the playback machine to minimize the effect, but there’s always an interval of getting up to speed.”

“And that’s what you detected?”

She nodded. “It’s called a windup signature.”

Sanders said, “And that never happens if the signal is coming direct from a camera, because a camera has no moving parts. A camera is instantaneously up to speed at all times.”

I frowned. “So these tapes are copies.”

“Is that bad?” Sanders said.

“I don’t know. If they were copied, they might also be changed, right?”

“In theory, yes,” Sanders said. “In practice, we’d have to look carefully. And it would be very hard to know for certain. These tapes come from a Japanese company?”

“Yes.”

“Nakamoto?”

I nodded. “Yes.”

“Frankly I’m not surprised they gave you copies,” Sanders said. “The Japanese are extremely cautious. They’re not very trusting of outsiders. And Japanese corporations in America feel the way we would feel doing business in Nigeria: they think they’re surrounded by savages.”

“Hey,” Theresa said.

“Sorry,” Sanders said, “but you know what I mean. The Japanese feel they have to put up with us. With our ineptitude, our slowness, our stupidity, our incompetence. That makes them self-protective. So if these tapes have any legal significance, the last thing they’d do is turn the originals over to a barbarian policeman like you. No, no, they’d give you a copy and keep the original in case they need it for their defense. Fully confident that with your inferior American video technology, you’d never be able to detect that it was a copy, anyway.”

I frowned. “How long would it take to make copies?”

“Not long,” Sanders said, shaking his head. “The way Theresa is scanning now, five minutes a tape. I imagine the Japanese can do it much faster. Say, two minutes a tape.”

“In that case, they had plenty of time to make copies last night.”

As we talked, Theresa was continuing to shuffle the tapes, looking at the first portions of each. As each image came up, she’d glance at me. I would shake my head. I was seeing all the different security cameras. Finally, the first of the tapes from the forty-sixth floor appeared, the familiar office image I had seen before.

“That’s one.”

“Okay. Here we go. Laying it onto VHS.” Theresa started the first copy. She ran the tape forward at high speed, the images streaky and quick. On the side monitors, the signals bounced and jittered nervously.

She said, “Does this have something to do with the murder last night?”

“Yes. You know about that?”

She shrugged. “I saw it on the news. The killer died in a car crash?”

“That’s right,” I said.

She was turned away. The three-quarter profile of her face was strikingly beautiful, the high curve of her cheekbone. I thought of what a playboy Eddie Sakamura was known to be. I said, “Did you know him?”

“No,” she said. After a moment she added, “He was Japanese.”

Another moment of awkwardness descended on our little group. There was something that both Theresa and Sanders seemed to know that I did not. But I didn’t know how to ask. So I watched the video.

Once again, I saw the sunlight moving across the floor. Then the room lights came up as the office personnel thinned. Now the floor was empty. And then, at high speed, Cheryl Austin appeared, followed by the man. They kissed passionately.

“Ah ha,” Sanders said. “Is this it?”

“Yes.”

He frowned as he watched the action progress. “You mean the murder is recorded?”

“Yes,” I said. “On multiple cameras.”

“You’re kidding.”

Sanders fell silent, watching events proceed. With the streaky high-speed image, it was difficult to see more than the basic events. The two people moving to the conference room. The sudden struggle. Forcing her back on the table. Stepping away suddenly. Leaving the room in haste.

Nobody spoke. We all watched the tape.

I glanced at Theresa. Her face was blank. The image was reflected in her glasses.

Eddie passed the mirror, and went into the dark passageway. The tape ran on for a few more seconds, and then the cassette popped out.

“That’s one. You say there are multiple cameras? How many all together?”

“Five, I think,” I said.

She marked the first cassette with a stick-on label. She started the second tape in the machine, and began another high-speed duplication.

I said, “These copies are exact?”

“Oh, yes.”

“So they’re legal?”

Sanders frowned. “Legal in what sense?”

“Well, as evidence, in a court of law—“

“Oh, no,” Sanders said. “These tapes would never be admissible in a court of law.”

“But if they’re exact copies—“

“It’s nothing to do with that. All forms of photographic evidence including video, are no longer admissible in court.”

“I haven’t heard that,” I said.

“It hasn’t happened yet,” Sanders said. “The case law isn’t entirely clear. But it’s coming. All photographs are suspect these days. Because now, with digital systems, they can be changed perfectly. Perfectly. And that’s something new. Remember years ago, how the Russians would remove politicians from photographs of their May Day line ups? It was always a crude cut-and-paste job—and you could always see that something had been done. There was a funny space between the shoulders of the remaining people. Or a discoloration on the back wall. Or you could see the brush-strokes of the retoucher who tried to smooth over the damage. But anyway, you could see it—fairly easily. You could see the picture had been altered. The whole business was laughable.”

“I remember,” I said.

“Photographs always had integrity precisely because they were impossible to change. So we considered photographs to represent reality. But for several years now, computers have allowed us to make seamless alterations of photographic images. A few years back the National Geographic moved the Great Pyramid of Egypt on a cover photo. The editors didn’t like where the pyramid was, and they thought it would compose better if it was moved. So they just altered the photograph and moved it. Nobody could tell. But if you go back to Egypt with a camera and try to duplicate that picture, you’ll find you can’t. Because there is no place in the real world where the pyramids line up that way. The photograph no longer represents reality. But you can’t tell. Minor example.”

“And someone could do the same thing to this tape?”