The smell is like nothing else. They'll tell you it's like a wet penny: a sweet, heavy tang that hangs in the air and lingers in the mouth, filling your throat with the familiar, coppery aftertaste of a licked coin. "Very unique," says Neal Smither, as if savouring the bouquet of an expensive claret.

The smell is like nothing else. They'll tell you it's like a wet penny: a sweet, heavy tang that hangs in the air and lingers in the mouth, filling your throat with the familiar, coppery aftertaste of a licked coin. "Very unique," says Neal Smither, as if savouring the bouquet of an expensive claret.

"Metallic," agrees Shawn Clark. "Like having a nine-volt battery on your tongue. The smell when it's fresh. Especially if it's a suicide."

The scent of spilled blood in a small room is unmistakable. And it will stay with you for hours. It's something about the way the brain works: how the senses are wired together, the molecular memory of the olfactory system. But there's another, simpler, reason why it's difficult to forget: it's the smell of death.

The men at Crime Scene Cleaners (CSC) know that smell intimately. They know the way it changes over time, how a body left undiscovered since Monday will reek by Wednesday; how it plateaus after a week or so; how when you wet down a dried stain it's reactivated right away; how the sugars in an alcoholic's blood make it different from that of someone with a regular diet. They know how hard it is to rid yourself of the stink of a decomposing body - even after you've showered, and you're at home eating your dinner, a whiff will drift up to you, faint but distinct. They return to it again and again, that smell.

Neal Smither's Crime Scene Cleaners has a simple legend painted beneath the company name on the side of its trucks: "Homicides, suicides, accidental deaths," it says, "24 hour service." They do a job few people know exists: a grim, practical necessity that across the US falls through the cracks between police and municipal responsibility. They tend to what's left behind by the suicides and the murders when the coroner and the detectives have gone, when the evidence has been collected and the bodies taken away. They come to scrub the bloodstains on the carpet; the fingerprint dust on the doorframes; the brain matter on the ceiling. It is, says Smither, something nobody really wants to contemplate: "When you think about your dying, you don't think about your becoming a puddle on the floor. That's not part of the whole process for you. It's too uncomfortable for most people to even consider."

I first meet Smither on a warm April morning in Orinda, a suburban Californian town in the green hills between Oakland and San Francisco. Smither is taking calls at CSC's corporate headquarters - a small room filled with cheap laminated furniture and box files, in a tidy clapboard building behind a mall. Smither sublets the room from his accountant. "It's a decent business address," says Smither, "Orinda is a good, affluent community - and I like to come to the office every day." Today, he and Shawn Clark - a big, laconic man in paint-spattered jeans, with orange-and-red flames tattooed in a band around his right forearm - are here to discuss the day's work. Clark is one of three cleaners Smither has in California: each of them works from home with his own truck, and is on call 24 hours a day, five days a week. And usually they work alone, unless a job is particularly demanding. Smither guarantees customers that one of his men will be on a scene within 60 minutes of their call: "I don't like to wait - period," he says. "I don't know about you, but if I've got a puddle of blood in my house, it's getting done that day."

Despite its name, CSC actually deals with all kinds of biohazardous mess. This includes decontamination of methamphetamine labs, clearing out "garbage houses"- where people have filled their homes with rubbish, human or animal waste - and elimination of the Hantavirus caused by rat infestation. It has contracts to clean for many of the local California police departments, to wash down jail cells or clean out squad cars, and national contracts - protected by non-disclosure agreements, "Because they don't want anyone to know how much we do for them or that we do it, period," says Smither - with several of the US's largest motel chains.

But in one way or another, most of Crime Scene Cleaners' work involves people dying.

"The majority of it is death. And then the garbage houses. But those usually involve death. And the meth. But..." says Smither, "we do a lot of death, man. A lot of death."

Later, he illustrates his point by spending 10 minutes reading through the work listed in a 3in-thick binder filled with company invoices for one month of 2003: "decomp... soiled carpet, body fluids... kitchen floor bloody... a suicide for sure... fingerprint dust - that was a murder... another murder... suicide, in a motel... this made the news - in Napa, steel beam broke and crushed a guy... you know, it gives you some idea," he says eventually, "most of it is gore."

Neal Smither likes to tell people that he's a Type A personality. "It means I'm very aggressive, and I'm not all that nice," he says. At 36, he's bullish about his company, macho about its work and studiedly abrasive in his manner: he says "negative" when he means "no" and swears with all the aplomb of an ex-serviceman. A high-school drop-out, Smither joined the Navy at 19, and spent nearly four years as a rescue swimmer - the man on a search-and-rescue helicopter crew who dives into the sea to save drowning airmen. It's famously one of the toughest jobs in the Service: rescue swimmers are one notch down from elite special forces troops like Navy Seals. Smither hated it: it wasn't the training or the demands of the job, he says. He just hated taking orders.

He was selling washing machines when he first had his business idea. At 27, he'd been working as a mortgage broker. It was a salesman's job - commission only - and he was good at it. He'd earn up to $200,000 a year; he ran his own division. But in 1993, the company was downsized, and Smither was laid off: "I figured, fuck! Now what?" He drifted from one thing to another: he scrubbed boat bottoms in Berkeley Marina, worked as a waiter and, in the meantime, tried to decide what to do with his life. He knew he wanted a secure job with a regular wage. And there was another thing: "I didn't really want to deal with a whole lot of people. I was burnt out, sick of people. I didn't want to talk to anybody - to kiss any more ass."

In the end, he thought he'd hit on the perfect job: he'd train to become a mortician. "I figured, I'm always gonna have job security. The ultimate goal for me was to become self-employed - to own my own mortuary." So he enrolled at the San Francisco College of Mortuary Science, and, while waiting for term to start, got a job in an appliance shop selling white goods. But one evening he rented a video of Pulp Fiction, and, when he reached the scene where Harvey Keitel enjoys a cameo as the dinner-jacketed Mr Wolfe, he was struck by a better idea. Mr Wolfe is called when two hit-men need the messy results of a killing scrubbed from the inside of their car. "And I thought, 'Man - that's a fuckin' good idea. I wonder who does do that?'"

What Smither discovered was, for a dedicated salesman, a totally unexploited market: "It's not like any product I've ever seen," he says. Historically, when a murder or suicide took place in someone's home, the friends or relatives of the victim - or, sometimes, a sympathetic police officer - would clean it up. And while there were a few companies who offered a professional cleaning service, they did little to advertise and conducted themselves with the quiet discretion of undertakers. "They don't want to offend or upset, or chase the money," says Smither. Naturally, he has no such qualms.

Keeping his day job, in June 1996 he bought a pager and a freephone number and began leafleting local mortuaries and - especially - police departments. "Any of 'em I could find in the Bay Area, from the ones with two or three officers to the ones with hundreds."

He took ads in the Oakland Tribune, but the paper received complaints and, after a while, it refused to run any more. "They were very tasteful, but they happened to be in the obituaries section and the older people read that every day. They got offended."

It took a month or so for his first job to come in. A woman called him out to a waterside apartment complex in Marina Bay: her sister had been suffering from cancer and come out of remission. "Blew her brains out. In her bedroom."

Smither was so excited that his business was taking off that he was blind to the brains on the ceiling, and simply set about cleaning it up with his off-the-shelf detergent, scrubbing brushes and paper towels. "I didn't care about the mess. I didn't care that the woman was dead. I mean, it was a terrible thing - but I was glad that someone had my number." He got his sister and wife to help him do the cleaning; it took them a couple of * hours. He charged the woman $250 (£130). "And she couldn't write me a cheque fast enough."

11.30am Monday. Business is slow. Over the weekend, three good jobs came in: two suicides and the accidental death of a man crushed while working under his car. But so far this morning, Smither's phone has only rung with one piece of contract work: San Jose Police Department has a squad car full of urine. "They arrest these fools," explains Smither, "probably after last call at the bars last night and he pisses all over himself." He calls Jake Hansen, CSC's man 60 miles away in San Jose, and sends him off to mop out the car. He will charge San Jose PD $50 (£30).

While we wait, Smither explains the parameters of the company's work. He talks about the most surprising job he's ever had - disposing of the corpse of a humpback whale stranded up an estuary canal. He quoted the county $9,000 (£4,900) for that, and then simply lifted the body out with a hired crane, drove it a few hundred feet down the road - beyond the view of the TV crews and whale enthusiasts who had gathered to watch - and buried it on public property. It took 20 minutes. "Beautiful," he says. He explains about the methamphetamine labs: the process of manufacturing crystal meth is so toxic and yet so simple that it's become an endemic problem for his motel-chain clients: "1lb of meth makes 50lb of waste. It's nasty shit." The company took on one job in Montana where the meth cooks had vented their lab through the hotel's heating system, and contaminated 19 other rooms with poisonous fumes: it cost $25,000 (£13,600) to clean up. He opens a stainless-steel suitcase beside his desk. It's filled with spent disposable cameras - 60 of them - used to photograph lab clean-ups in case of legal action: "This is last year's meth labs, only for hotels - and only one chain."

The things Smither has seen in the course of his work have not led him to a positive view of humanity. "I hate people more than I ever have," he says. "I'm pretty cynical. About 80 per cent of everyone we deal with is a borderline scumbag. You know - you let grandma die on the floor and rot for 60 days, then the janitors are cleaning, and you get to the house and start fighting over her belongings? That classifies you in my opinion as a scumbag."

Does that happen a lot?

"Oh, all the time. All the time. Or just the way they live, you know? It's very common for us to go into a house that's three-, four-, five- feet deep in trash. Little canals everywhere. They're shitting in buckets on the floor. They live like animals. It's very common. We've done thousands of 'em."

From his desk drawer, he pulls a sheaf of Polaroids taken inside garbage houses, and hands me one.

"Here's a good example - that's a bathroom. That brown stuff ain't mud."

The scene in the picture is so disgusting, I gag.

"Yeah," says Clark, "that was extreme. We literally had to use shovels."

Later, Smither and I will have lunch together, at a cheesesteak-sandwich shop in nearby Walnut Creek. From his pocket, he produces a small bottle filled with transparent gel: it's an alcohol-based hand sanitiser, which he rubs over his palms before the food arrives. He's been using it for a while now - "Religiously for the past year." He prefers it to washing his hands in sinks used by other people: "You just don't know, man," he says. "I tell you - this job'll do it to you." These days, he won't even wear shoes inside his own house. "All the things you walk in without realising it," he shudders, "Ugh!"

When I leave him that afternoon, Smither still hasn't had any more work come in; he does not say goodbye. Instead, he leans from the window of his truck and shouts, "Pray for death!". And then he gives me a cheerful wave.

Smither's winning new business idea did not take off immediately. In fact, after his first job, his phone rang again only twice in a year: "I was desperate: going broke." The first call was to scrub blood off the street after a road accident in San Jose. In increasingly litigious California, police and fire departments often refuse to hose bloodstains off the road and into the drains - because the blood will wash, untreated, straight into the Bay. "And the environmentalists all go crazy," Smither explains.

The next job he remembers vividly: "It was off the chart," he says. " Very severe. I was way over my head, knowledge and skill-wise." Smither was summoned to a block of flats in Oakland, where a tenant had committed suicide. "It was a big, fat guy - taken pills, killed himself. Left a note, sat on his couch and decomposed. It was summertime - hot. Very hot. Better than 100 degrees every day."

By the time Smither arrived on the scene, the man's corpse had been removed by police - but it had been sitting in the flat for weeks, and his neighbours had been forced out of the building by the stench. "I get there," he says, "and you can smell it from the street." Smither had no experience and no real idea of what he was doing, and entered the flat with the intention of simply removing the couch on which the man had died, and the carpet beneath it. Now, he explains, he understands more about the process of decomposition. Shortly after death, rigor mortis sets in throughout the body - but after 12 hours or so, the corpse relaxes. "Then your fluids start to purge. Everything from cranial fluids, spinal fluids, your stomach - you're primarily liquid, and it starts to come out of your body. That's the stuff that's just... terribly noxious. Your skin is porous. It will leak out of your butt, mouth, ears, eyes. You leak," he says, "big time."

Smither and his sister were unaware of this when they began to manhandle the putrid sofa out of the flat. When they reached the doorway, they tipped it on end: with regrettable results. "It released a torrent of fluids all over the floor."

Smither's sister vomited immediately. But he himself was so panicked by the mess that he didn't give himself time to be sick: he just wanted to get the sofa out of the building as quickly as possible. In the end, they got it to the truck, drove it to a landfill site, dumped it - and got paid. Smither has still never come across anything that has actually made him physically sick. "I've gagged," he says, "but I've never puked. And I've never looked at anything and gone, 'Oh my God!' I've looked at it and gone, 'Oh yeah: the price is right.'"

By 1998 - when California state enacted strict legislation requiring death scenes to be cleaned by a registered blood-borne pathogen mitigation company such as CSC - Smither was doing enough work to be able to hire his first employee. Now, including the one in California, the company has offices in 11 states across the country. In a month, CSC will do between 300 and 600 jobs in the Bay Area alone. The annual national turnover of the company is around $3m (£1.6m).

In the beginning, Smither went through a lot of employees in a very short time: "If they made it to six months," he says, "I was overjoyed." And even now, getting the right people is difficult. "I like them to be anal retentive - Type A helps. Goal oriented. They have to be fairly unique. I don't bring 'em in for a fuckin' interview. I make 'em chase me, jump through so many hoops that if they're still with us, begging for a job, I'll hire 'em." He receives hundreds of applications. But few of them are right for the work.

There are the freaks, of course: the tattooed and the pierced, the Goths and the death-metallers. There are those who come thinking they're going to earn a fortune: "That it's such an extreme job that it must pay out the ass," says Clark. "It's not the case." Then there are the plain desperate. "The toothless wonders, you know - they look like life's just dealt them a bad blow, and they think, 'I can do that; I've been through so much horrible shit in my life, I can handle that.'" Whenever Clark goes to clean jail cells, the inmates always ask him for work.

For some people, the work simply exerts a grim fascination. Smither is often chased down the motorway by people who see the name of the company on his truck. "We have groupies," he explains. "People will follow me down the freeway to say, 'I saw you on TV!'"

"What I don't like," mutters Tom Silva, * "is when I have 20 to 30 people that walks up to my truck every other day and says, 'Hey - is that for real?' Now that's kind of irritating. You think, OK - if my truck said 'plumber' on the side of it would you say, 'Hey - is that for real? Are you serious?'"

Silva is 27 - a tall, rangy man with a neat moustache and cracked, yellow teeth. He's CSC's longest-serving employee having started working there in 2000 after doing some labouring jobs at Smither's house. He lives nearby in Richmond - "Not a good community. A ghetto," he says. "You understand what one of those is?" He grew up there, the only white kid in an otherwise entirely black area. He saw his first death when he was seven years old, when a Sunday morning argument in a pool-hall carpark ended with someone pulling a shotgun: "I saw a gentleman get shot with a 12-gauge and get half his side blown off." He got used to that kind of thing early on. Out of his junior-high-school class of 60 pupils, he reckons he is one of only nine who aren't dead or in jail. But he didn't want to run the streets like the others: "Just had a smarter head on my shoulders, I guess. Decided to do something better with my life."

Silva enjoys the crime scene work because he sees something different every day. "At Starbucks," he says, "they have to sit and look at people for eight hours and stand in the same place. I couldn't do that... I don't think I could do anything else after this." Smither tells me that Silva is exceptional; the most loyal and hard-working man he has. Even so, there are some jobs that he can't do for the company - cleaning some jail cells, for example - because of his criminal record; at 17 he was convicted of burglary. "If he wasn't a felon," says Smither, "he'd be my best employee."

Within a month, however, Smither will tell me he's had to let Tom go - since he shot a man in the chest, and went on the run, wanted for attempted murder. Smither didn't even get to clean the scene: "I wish I did," he says. "The least he could have done was made me some money."

5.55pm Wednesday. At the end of a long day spent driving the length of Highway 101, visiting police departments to drum up business, gladhanding desk sergeants, handing out promotional T-shirts and leaflets, Clark has just had a call from Smither. It's a suicide - a gunshot to the head - in Campbell, 50 miles back in the direction he's just come. Clark was only a few miles from home when the phone rang. "I'm hoping this guy was considerate," he mutters, "'cos I'm kind of burnt out. I'm hoping it's not more than an hour. It depends: if it was a shotgun - if it was a shotgun, then..."

Clark and his colleagues rarely know any details of a job before they arrive on the scene: all they get from Smither is an address and the type of problem it is. They have to estimate the cost themselves when they arrive. CSC charges for a job are based on "severity": they start at $300 (£160) and rise to the top rate of $1,875 (£1,000), depending on how long and involved the clean-up will be. Natural death decompositions are pretty expensive; but shotgun suicides are among the most highly priced jobs they do. Brain matter is particularly difficult to clean up: it dries as hard as marble; and the physics of such a death creates a terrible mess. "The muzzle velocity literally blows their skulls apart," says Clark, "and that stuff flies and hides. You have to look at the wall and the bounce pattern - you could have bits and pieces behind the bed, the sofa, or down the hallway, in a bathroom around the corner."

Shawn says that the next month-and-a-half will be busy for him - it's tax time. Last year, he had to clean three identical suicide scenes in different houses - in the home office, the computer still on, spectacles laid on the desk, the bills all fanned out.

"You could tell they'd just been crunching the numbers and thought, 'Fuck!'"

At 31, Clark has been working for CSC for two years. He studied psychology and art history at San Diego University, but, months before graduation, a professor walked into his class and announced that anyone there who was studying psychology to better understand themselves should leave immediately. "So I got up and walked out." Since then, he's sold computers for Hewlett-Packard and did market research until his job disappeared when the Bay Area dotcom bubble burst. He was working as a landscape gardener when one of his clients suggested he talk to Smither about a job: "For me, it was something new. Then, honestly, I didn't know if I could do it."

It's a long drive to Campbell, and by the time we arrive it's dusk. The house is in a respectable-looking neighbourhood, with boats and muscle cars in the driveways. I've become quietly nervous about what we might find. "It's gonna be off the chart - I know it," says Clark. "I've just got a gut feeling. This should be interesting. I'm interested in you seeing this."

Opening the front door into a dim, open-plan kitchen-diner scattered with the everyday debris of family life is Aaron, a stocky man in his late thirties. He's a friend of the family: he knows the dead man's wife. "She's my co-worker," he explains. "Her husband did... the number this morning."

We walk down a hallway and stand before the door to the bathroom. Clark carefully pulls on a pair of yellow rubber gloves, and places his hand on the knob. As the door swings inwards, I hold my breath.

Inside, there is a white bathtub, with a shower screen, and a sink. A bookcase beside the bath is stuffed with novels and pop science reference books - The Top Ten of Everything 2003, An Introduction To Quantum Mechanics - and, on top of the cabinet, within arms' reach of the bath, a copy of Ayn Rand's dystopian fantasy Anthem, folded open to the first few pages. The room appears to be comfortably disordered, but clean, as it would be if someone had just spent an hour luxuriating in the bath. And then Clark pulls back the shower screen: we both get a shock.

"Uh... Aaron?" Clark calls out, an edge of disbelief in his voice.

"Do you want me to come in there?" Aaron replies, hesitantly, from the kitchen.

The bath and surrounding tiles bear no sign of any bloody trauma at all. We lean over the tub, and peer closely at the enamel. There is a single spot of something which may be blood - but could just as easily be something else - clinging to the edge.

"This is a bust!" mutters Clark, gathering his cleaning enzyme and towels from the truck. He wipes the brown speck from the bath, and checks that Aaron is feeling alright, and knows about grief counselling. He hasn't the heart to charge for what he's done. Sometimes, when people are really serious about it, he explains, they'll wrap themselves in towels, blankets, or perhaps a sleeping bag, before shooting themselves - to save others having to clean up the mess. And if they use a small-calibre gun, like a .22, the bullet will enter the head but not exit: "It'll just scramble your brain." But he's never seen anything like this before: the police or the coroner must have cleaned the scene up before they left.

Now it's late, and Clark is faced with a 60-mile drive home. He's already told his fiancée he won't be home for dinner. He's furious. "The dude could have at least looked!" he says, as we pull away. "Wasn't he even curious?"

The men at Crime Scene Cleaners have learnt a few things from doing this job. Smither says that you usually find the same three things at the scene of a suicide: "Porno, drink or drugs - and a weapon." Men prefer to kill themselves using firearms; women, knives. Often you can see from the pattern of bloodstains that someone has slit their wrists and then panicked, reeling around the room, touching things: "They see the blood and go, 'Holy shit! What have I done?'" And the scenes of suicides are almost always dimly-lit: "Most of these people are filthy and live in the dark. One fuckin' lamp over in the corner. A 40-watt bulb, you know? Turn some lights on! You might not kill yourself!"

They say that drinker deaths are the worst: the way the alcohol eats into the liver until there is one final, fatal haemorrhage. Clark remembers cleaning one scene in Fremont where an alcoholic had drunk himself to death in a motel room. The cop on the scene told him that when they found the man's body, he still had a screwdriver in his hand. Shawn couldn't understand why a man would die using a screwdriver until the cop explained: "The drink. It was vodka and orange, and he was just sitting there dead with a drink in his hand, in his own bathroom. All of his body fluids just blew out of his ass." Clark gave up drinking soon afterwards.

Like each of the men he works with, at first Smither was eager to find out the details behind each job: the stories of the dead; the explana-tion for each suicide; the arc of a life cut short by murder, or why an old man's body was left undiscovered for weeks. "When you first get into the game," he says, "you want to know everything. I mean, you really do." But after they've been doing it a while, ask any of them about the details of particular jobs, and they'll have to think hard: "Don't know", they'll say, or "Didn't ask"; or, perhaps, "Didn't care." * There are those who have been fixated on the details of each case - like the pierced and tattooed kid Smither once hired who tried to steal a blood-spattered print of The Last Supper from a suicide scene - but they don't last long. If you're in the job long enough, the number of deaths will simply overwhelm you. "It's that many," says Smither, "that - one, there's no way to remember, and - two, if you did dwell on each one, you'd lose your mind. You just don't see it after a while." Eventually, the scenes themselves all run together: "They're all basically the same. Bloody carpet. Bloody furniture... after a while you don't even see the blood. When you're leaving, you've already forgotten the job - if you're good at it."

"You can't be the sort of person that focuses on the death part of it," Clark will tell me. "If you get hung up on that, it'll eat you up. If you're superstitious, or incredibly religious, I don't think you can do this job. Other than that, you're just cleaning. It's almost self-explanatory. It's dirty - clean it."

9.25am Saturday, 32 Gumtree Apartments, 2124 Park Avenue, San Jose. The blood on the wall of the bedroom forms two thick, dripping stripes, as if carelessly daubed there with a creosote brush. It has run down into the corner, soaking the carpet with a foot-long stain that's dried a deep red, almost black. The smell of the blood mingles in the air with the stagnant, sickly odour of a shuttered room gone uncleaned for too long. The cheap, two-room flat is filthy and cluttered; the surfaces and door-frames smeared with aluminium fingerprint dust. Inside the front door, the police have stacked the mattresses on which the woman died: all three are stained with dark patches of blood ringed with pale shadows of plasma. The carpet will have to be cut out; the walls scrubbed; the mattresses and linens dumped. Jake quotes the whole job at $675 (£360) - maybe $475 (£260) if he wants to make sure he gets it.

Jake Hansen is 30, and, with under a year on the job, Smither's most recent hiring. Baby-faced and affable, he came to the company after doing his three-month training as an emergency medical technician - a step on the way to becoming a paramedic, which would have enabled him to drive an ambulance. He's also qualified as a plumber - "I was ranked number one in the state of Washington," he says, "for my drain-cleaning abilities" - and spent a while in rehab after seven years addicted to, and dealing, crystal meth. Now he lives with his parents in San Jose; he hopes the job with CSC will take him into law enforcement, or maybe the fire department.

This is the end of a quiet week for Hansen. All he's done since Monday is clean a couple of squad cars, do a little PR around the police departments and scrub down the tables at the morgue. He's spent most of the time at home, watching TV. "I've put on 20lb just waiting around," he says. But he tells me something always happens when he makes other plans: "It's like they focus on when you're trying to have fun... death comes calling."

This one, he's been told, is a murder - an old woman shot in bed during a burglary. "Pretty basic," he says. "Typical." Outside, he pulls on his tieback - a bright blue disposable booted overall with elasticated cuffs and a hood - and a pair of rubber gloves, and sets to work on the blood.

But as I look around the squalid rooms - and the disarray left by the crime and the investigation that followed - it seems less and less likely that an old lady lived here. There's the head of a butane torch and a scorched Pepsi can, which have been used for smoking crystal meth. There are three dried-out slices of pizza on a plate in front of the video recorder, which contains a tape of infamous 1970s gang movie The Warriors. Beside it is a pile of R&B CDs, and a ceramic sign which reads: "Beware of the pussy!" Here and there are photos: on the walls, of a little girl playing in a park and, on a cabinet, in a metal frame decorated with tiny metal heart pendants, another of a blonde woman holding a newborn baby. "Hot, too," says Hansen approvingly.

Gradually, we begin to realise that it is probably the woman in the photos whose blood is everywhere. She can't have been more than 25. This uncertain realisation, and the way it dawns, pieced together from trash, snapshots and junkie paraphernalia, makes the whole scene - and the task we're here to do - impossibly bleak.

But Hansen, on his hands and knees, spraying the blood on the wall with cleaning enzyme, is impassive when I ask if any of this bothers him.

"No," he says flatly. "It's like cleaning up spilled milk."

On the floor, amid the debris - a San Jose PD-branded envelope still wet with blood, children's shoes - I find a small hard-backed book of the kind they sell beside the till in bookshops. It has a picture of Mickey Mouse and Pluto on the cover, climbing a mountain; Pluto dangles helplessly from a rope, while Mickey hauls him up. It's called Hang In There, and is filled with rhyming couplets: upbeat messages to make yo