Picture a crime, any crime. No matter whether it's a burglary, a body found in suspicious circumstances or a sexual assault, one thing remains constant. The incident spot will be fine tooth-combed for any forensic or fingerprint evidence by police scenes of crime officers, writes crime reporter Emma Henry.

Civilians, but working in close harmony with investigating officers, a day in the life of a scenes of crime officer can see him or her dusting down doors for fingerprints after a burglary or collecting forensic evidence such as hairs and body tissue samples left at the scene for future DNA testing.

More unusually, but not uncommonly, scenes of crimes officers socos in police-speak have the grim task of collecting and recording evidence if a body is discovered and suspicious circumstances suspected. And they never know what will greet them as they start each day. My guide for a day is to be St Aldates Police Station-based soco Nick Hatt, one of a team of five covering the Oxford area, including stints on-call at night.

A married father-of-two from Witney, he has been a soco for 12 years and worked at the scene of many high-profile city murders, including that of St Hilda's student Rachel McLean in 1991 and the unsolved 1994 shooting of Oxford University medical researcher Dr Michael Meenaghan in his Blackbird Leys home.

"The job of a soco is basically to record a crime as it is. We photograph it, sometimes use a video, and then gather evidence. That can take minutes or hours, depending on the crime. For a rape or a murder we can be in the house for a week and we might take up to 40 rolls of film.

"Everything we take from the crime scene is catalogued and has to be kept for a minimum of seven years. Films and fingerprints go to specialist units at Kidlington police HQ and forensic evidence goes to a Home Office laboratory near Culham," says Nick. "Once we've logged the evidence, we don't have a great deal to do with it and results are passed on to the officer in the case."

Surely constant exposure to violent crime must take its toll on emotions? But Nick's dismissive of this, saying: "I don't think it affects me I put it in a little box somewhere, I suppose.

"We've just started having debriefs, and a few people do go off with stress. But you get used to it. Once you've seen a few bodies, there's nothing new and you just get on with the job. It's not like with paramedics, where you might be able to do something for them and have to live with it if you don't. Having said that, there have been a few gruesome ones, particularly a triple murder where bodies were found in both Nelson Street and Marston."

But today's jobs, requested for crimes reported to officers on the night shift, yield a raft of burglaries and attempted break-ins, along with stolen vehicles the bread and butter work for socos.

They will be supplemented throughout the day as other crimes are reported or take place. The first task is to photograph a young woman who has been left with a black eye after an assault in the city centre. She also has extensive bruising on her arms, but is unsure about whether she wants to press charges. Nick takes a series of photographs cataloguing her injuries, in case she does decide to go forward with a prosecution.

Nick says: "All socos are sent on an intensive course to learn the three disciplines of forensics, photography and fingerprints technology, and we're tested all the way through. We also use special large negatives, so the pictures can be blown up easily."

These films, like others taken, will be couriered to the developing lab at Kidlington HQ and then given to the investigating officer.

Then we hit the streets and the first stop in our unmarked van is a house in north Oxford, where a man was arrested the night before after a young woman living in the house saw him standing outside staring at her and then peering in through the door.

Nick talks to the young woman to work out where the man is most likely to have left his fingerprint or forehead marks, and then sets to work, brushing the front door glass and the back window with aluminium powder. As fingerprints are essentially sweat imprints, he tells me, the powder sticks to the outline, colouring it so a copy can be lifted. The more recent the crime, the clearer the print. The brushing pays off on the front door, with several clear fingerprints successfully lifted.

But they could belong to any of the people living in the house, so the woman and her housemates are supplied with do-it-yourself fingerprint kits to send back to police to eliminate their prints from the inquiry.

The next two jobs, a room break-in at Wadham College and vandalism at a city centre estate agents, are not so productive. Despite extensively brushing the likely points of entry, no clear prints can be lifted.

"The problem is often that lots of people have used the same door, or the surface is not smooth enough to capture the print," explains Nick.

But our next job is more successful 3,500 in cash has been stolen from the safe of a north Oxford firm, and there are lots of fingerprints on the cash tin, including two particularly clear ones. Nick dusts all around the door and the cash tin, takes away an envelope left in the safe for chemical testing and again leaves DIY fingerprinting kits for the members of staff.

Back at the office, the envelope is dipped in Ninhydrin, which reacts with sweat to find fingerprints on paper and natural wood, before it is placed in a special oven to dry. The chemical is banned from sale to the general public, but the police have a special licence to use it as it is the most effective for this task.

Again a good result several prints show up on the envelope, which is stored in a plastic envelope ahead of its journey to the fingerprint bureau at Kidlington in an attempt to find a match with others which are already on file.

Today is a quiet day, mainly burglaries and no major crimes to speak off, so Nick takes a chance to catch up on his paperwork.

Four copies are needed of every crime scene report, including one for the computer as a backup. Even with technological advances, paper copies still go to the officers involved in the case. But as he works, he is aware that at any moment that emergency call could come in, shattering his peace and quiet and leading him back into the grisly aftermath of murder or mayhem.

Socos were once police officers but are now highly trained civilians. They have absolute authority at crime scenes, even being able to order police officers out of a room or area if it is affecting evidence gathering.

When Nick Hatt decided he wanted to go into scenes of crimes, he moved from the fingerprint bureau at Kidlington, where he had qualified as an expert.

But now most new entrants for the job, which has a salary of around 20,000, are graduates, and have to attend a nine-week residential training course in Durham to learn their trade.

Evidence can be seasonal, with more fingerprints found in the summer and more footprints in autumnal months when the ground is softer. Footprints are recovered by pouring a solution similar to plaster of Paris into the imprint and making a cast.

Socos' written records can be used in court and they are often called on to give evidence at crown court trials about details of a crime scene.