Page last updated at 11:27 GMT, Wednesday, 2 December 2009

Forensics machine to boost hunt for bomb fragments

By Paul Rincon
Science reporter, BBC News, Fort Halstead, Kent


Machine helps to find bomb clues

The guidance for visitors informs us that we will receive a warning prior to the detonation of an explosive device.

It urges us not to be alarmed and to "be prepared for a bang".

The advice is welcome, if not entirely unexpected. It's a reminder of the vital and hazardous work carried out here at the UK's Forensic Explosives Laboratory (FEL).

Situated in Kent's leafy North Downs, FEL is the world's oldest forensic science laboratory, established 130 years ago.

Though it operates under the aegis of the Defence Science and Technology Laboratory (DSTL), the large part of its work is with police forces.

With more than 60 staff, the high-security lab deals with all types of incidents involving explosives.

Sifting through tonnes of debris left in the wake of an explosion is not an easy job
Garth Shilstone, DSTL

These range from rash experimenters using improvised chemical mixtures right up to major terrorist attacks such as the London bombings of 7 July, 2005.

The lab's work is usually kept out of the public gaze, but insights have emerged when FEL scientists have been called as expert witnesses in trials.

For example, following the botched London bombings of 21 July, 2005, and the two car bombs parked in the West End in 2007, FEL researchers blew up replicas of the devices to test their explosive potential.

Specialists use a variety of scientific techniques to characterise explosives, their residues and the components of a device, providing valuable evidence in a police investigation.

After arriving at FEL's complex at Fort Halstead, near Sevenoaks, we are escorted to a briefing with Phil Morley, team leader in forensic support.

Mr Morley, an engineer by training, runs the facility we have come to see - a brand new machine designed to sort through debris from explosion scenes.

Screening machine (BBC)
The dry debris is poured into a drum for screening

The machine is housed inside an anonymous brick building with a shuttered façade. Set on two levels, large metal drums and ducts gleam under the strip lighting. The equipment is operated by two men wearing white overalls, blue hard-hats and face masks.

The facility will enable large quantities of rubble from a crime scene to be quickly sifted and sorted into different sizes, preparing fragments for examination by forensic case officers.

Security minister Lord West was visiting the new processing facility as part of a general overview of FEL's work. He told BBC News: "When you think of a dreadful explosion such as the one on the tube system [on 7 July 2005]… there was so much debris, so much stuff to pull out, go through and sift. It has to be done very meticulously."

Designed from scratch

Dr Garth Shilstone, FEL group leader, comments: "Sifting through tonnes of debris left in the wake of an explosion is not an easy job, but it is vital in order to gather forensic evidence that could point to the cause of an explosion."

The equipment previously used by FEL was derived from agricultural machinery and required more manual handling. A few years ago, after the 7/7 bombings and the failed 21/7 suicide attacks, DSTL staff were asked to outline requirements for a new debris processing facility.

Services provider Serco was contracted to build it with Home Office funds of £500,000 over two years. Among other things, the requirements emphasised operator health and safety and the environmentally friendly disposal of waste.

Examination of explosion debris (BBC)
Millimetre-sized fragments are examined in fume cabinets

"Debris comes to us from a crime scene via the police. The police will normally carry out a pre-sift activity, so we'd only receive material that needs finer examination," explains Mr Morley.

Wreckage may arrive at the facility in discrete or large quantities, but it is usually wet, having being hosed down at the crime scene. Red plastic boxes are filled with up to 25kg of debris and raised to the facility's mezzanine level where the contents can be "tumble dried" in modified cement mixers.

The modifications include new motors allowing their speed to be regulated. They are also equipped with de-humidifiers and extractors to assist the drying process.

Once they have finished drying, the fragments are poured into a screening machine on the ground floor. After activation, the machine's vibrating drum produces a thunderous sound; we are handed earplugs before being treated to a demonstration.

Inside the drum, debris is separated into different grades based on the size of the particles. There are three grades - 12mm, 6mm and 2mm.

The facility has two of these screening machines, which can be used in tandem. But they would only process debris from the same crime scene in order to prevent cross-contamination.

Electronic debris (BBC)
Staff look for items that "don't belong" in the background environment

After sorting into different grades, the rubble passes through separate ducts to a forensic examining room next door. Here, technicians scour the debris by hand in ventilated search cabinets.

Each cabinet has a differently coloured worktop to assist with visual discrimination and is equipped with a magnet to quickly identify fragments of metal. Mechanical elements of the bomb such as the remains of timing devices or wires could potentially be linked to a suspect by police.

Phil Morley acknowledges the possibility that human tissue could find its way into debris handled by the facility. He says staff members receive appropriate inoculations and support from an onsite occupational health team.

Out of place

Mr Morley's team works on behalf of a forensic case officer, who is responsible for the crime scene material. At the beginning of the sifting process, the case officer will have briefed the search team on the background environment from which the material has come.

"We're not looking for anything specific, we're just looking for things that are alien to that background environment," Phil Morley explains. When team members find fragments that "don't belong", they put them aside for a case officer to assess in detail.

Case officers undergo rigorous training for a minimum of four years to equip them with skills necessary to safely handle explosives and to examine bomb debris.

The DSTL laboratory has a scientist on-call 24 hours a day to advise UK police services on explosives. Scientists from FEL can be deployed to the scene of an incident on police request.

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