'Dr. Jonas' - and it was Commander Penn who spoke - 'this is Dr. Kay Scarpetta, the chief medical examiner of Virginia and consulting forensic pathologist for the FBI. She is quite familiar with preserving crime scenes.'

Dr. Jonas looked up and I caught a glint of surprise behind her face shield. I detected embarrassment in the long moment it required her to read the chemical thermometer.

I leaned closer to the body, paying attention to the left side of his head.

'His left ear is lacerated,' I said.

'That probably happened when he fell,' said Dr. Jonas.

I scanned the surroundings. We were on a smooth concrete platform. There were no rails to strike. I shone my light over concrete supports and walls, scanning for blood on any structure that Davila might have hit.

Squatting near the body, I looked more closely at his injured ear and a reddish area below it. I began to see the class characteristics of a tread pattern that was wavy with small holes. Under his ear was the curve from the edge of a heel. I stood, sweat rolling down my face. Everyone was watching me as I stared down the dark corridor at a light getting closer.

'He was kicked in the side of the head,' I said.

'You don't know that he didn't hit his head,' Dr. Jonas said defensively.

I stared at her. 'I do know,' I asserted.

'How do we know he wasn't stomped?' an officer asked.

'His injuries are inconsistent with that,' I replied. 'People usually stomp more than once and in other areas of the body. I would also expect there to be injury to the other side of his face, which would have been against the concrete when the stomping occurred.'

A train blew by in a rush of warm, screeching air. Lights floated in the distant dark, the figures attached to them shadows with voices that faintly carried.

'He was disabled by a kick, then shot with his own gun,' I said.

'We need to get him to the morgue,' the medical examiner said.

Commander Penn's eyes were wide, her face upset and angry.

'It's him, isn't it?' she said to me as we began to walk.

'He's kicked people before,' I said.

'But why? He has a gun, a Clock. Why didn't he use his own gun?'

'The worst thing that can happen to a cop is to be shot with his own gun,' I said.

'So Gault would have done that deliberately because of how it would make the police… make us feel?'

'He would have thought it was funny,' I said.

We walked back over rails and through trash alive with rats. I sensed Commander Penn was crying. Minutes passed.

She said, 'Davila was a good officer. He was so helpful, never complained, and his smile. He brightened a room.' Her voice was clenched in fury now. 'He was just a goddam kid.'

Her officers were around us but not too close, and as I looked down the tunnel and across the tracks, I thought of the subterranean acres of twists and turns of the subway system. The homeless had no flashlights, and I did not understand how they could see. We passed another squalid camp where a white man who looked vaguely familiar sat up smoking crack from a piece of car antenna as if there were no such thing as law and order in the land. When I noticed his baseball cap the meaning didn't register at first. Then I stared.

'Benny, Benny, Benny. Shame on you,' one of the officers impatiently said. 'Come on. You know you can't do this, man. How many times are we going to go through this, man?'

Benny had chased me into the medical examiner's office yesterday morning. I recognized his filthy army pants, cowboy boots and blue jean jacket.

'Then just go on and lock me up,' he said, lighting his rock again.