"This is a crime," he declared as he stood up again, brushing the dust from the knees of his faded blue combat trousers. "It's just happened. This is fresh." We stood together in regretful silence, gazing at the scattered remains of the victim, which had been chopped up by someone with an axe.
"You know, this was a good tree," said Sgt Sergei Molodkin, smelling the warm wood shavings again. "It probably took 50 years to reach that height and now it's been chopped down in a minute or two." He shook his head in uncomprehending disgust and ran his boot over a chunk of the fallen lime.
A few yards away, the axeman was prowling around the wooded courtyard where the tree had once stood alongside a dozen or so silver birches, now also reduced to six-inch stumps. Until today, these had helped to provide a canopy of shade for the occupants of the shabby, sweltering Moscow apartment block near by, some of whom - old women in floral dresses and ankle socks - had gathered in the yard to glare at the axeman.
He was Viktor, an elderly, wild-eyed man in a pink T-shirt. He was bellowing defiantly at the sergeant's two partners, untroubled by the pistols that hung from their belts. "This wouldn't happen in Los Angeles," grumbled Sgt Molodkin, as the argument grew still louder. "We would have shot him by now. But here in Russia, you can insult us, shout at us, do practically anything." You wouldn't know, at first glance, that Sgt Molodkin is an Eco-Cop, one of a small band of warriors in the front line of the war against pollution in one of the world's unhealthier places, a city dotted with radioactive hotspots, the legacy of the Soviet Union's arrogant indifference to the environment. In fact, you cannot tell him apart from any other Moscow policeman but for the green logo on the side of the battered Zhiguli car in which he and his colleagues travel around their patch in the eastern part of the capital.
A few minutes ago, after rattling painfully slowly through the streets in response to a call-out, we pulled up here, at this apartment block on Izmailovsky Shosse, to investigate a neighbour'scomplaints that someone had chopped down a dozen of Moscow's 30 million trees without obtaining permission.
The scene of the crime - the stumps, the angry old ladies, the guilty- looking but unremorseful Viktor - told the story. The sergeant said it bore all the hallmarks of a familiar conflict: a war between Moscow's rapidly growing number of car owners who chopped down trees to make parking spaces for themselves in a city never built for cars, and non-car owners - the indignant old ladies.
Viktor was booked and a second team of inspectors was summoned to gather scientific evidence. He would, said the sergeant, probably be fined. Sgt Molodkin looked disappointed: he would have preferred Viktor to do forced labour, replanting the city.
This was our second bust of the day. An hour earlier, we had raced on foot into the woods of a city park to nab a group who had built an open fire to roast kebabs. The culprits were stunned to discover they were doing anything wrong. But the cops were adamant. There were more bookings, more likely fines.
This was, the cops later told me, a typical day for Moscow's ecology police, a body of only 730 staff that has been trying to clean up in the city. When it was founded in October 1996, it was the only such force: now there are 16 more around Russia. Their brief is extraordinarily wide - from catching illegal fishermen and the owners of unmuzzled pit bull terriers to cracking down on cars with illegal exhaust emissions or factories that poison rivers with waste. Their short history contains colourful episodes: catching a bear roaming in the woods and investigating an incident in which a schoolboy poisoned his classmates with a stink bomb.
Being taken seriously is a tall order in a capital that has plenty of more serious problems to worry about - such as 617 murders in the past six months and a flourishing underworld. But the Eco-Cops seemed genuinely, uncynically, committed.
"See this?" said Capt Sergei Bloshenko, 29. He was flourishing a photocopy showing pictures of flowers and fauna. "These are in danger of dying out. But we are trying to stop that. Every team in our force carries the pictures with them." Their target, he explained, were people who sold these flowers at Moscow's metro stations. "If we don't do something, who will? Our children won't have anything, will they?" he asked, with genuine emotion.
Call it what you like. Spitting in the wind. Closing the door after the horse has bolted. But you can't knock them for trying.