Over 400 exhibits, samples and items have been recovered by search teams as part of the ongoing police investigation into the murder of Dawn Sturgess and how Charlie Rowley was also poisoned by a Novichok nerve agent in Amesbury, Wiltshire.
On Friday, 13 July, the investigation team announced that they had recovered and identified a small bottle, which they believe to have been the source of the contamination.
However, searches are still expected to continue for several weeks, if not months as officers look to identify any other potential sites or sources of contamination, as well as gather further evidence to assist with their investigation.
Assistant Commissioner Neil Basu, National Lead for Counter Terrorism (CT) Policing in the UK, said: “It is not an exaggeration to say that the search process linked with both this and the Salisbury investigation has been one of the most complex and difficult that UK policing has ever faced.
“The work being carried out is extremely important. Not only are we trying to solve an extremely serious crime that has been committed, but we’re also working to identify any potential outstanding risks to the public; all whilst ensuring that all those involved in the search process are not themselves exposed to any risk of contamination.
“It is painstaking and vital work, which unfortunately takes a very long time to complete, but I am sure that the public understands why it is absolutely necessary.
"The scientists and forensic officers have all volunteered to be a part of the search teams, knowing that they are risking themselves to exposure to a deadly nerve agent. This shouldn't be taken for granted and their bravery and dedication is remarkable."
Planning for each and every search deployment takes several hours; identifying what evidence needs to be captured during the search and then deciding how this will be done. This work is led by the Forensic Management Team from CT Policing South East, in close consultation with scientists from the Defence, Science and Technology Laboratory (Dstl) and the police forensic officers from the National CT Network.
The search team carefully plans the equipment needed to achieve the aims of each search and how the samples or items are to be safely recovered and transported back to the Dstl labs at Porton Down for analysis.
Typical work involves taking swabs of surfaces or the recovery of specific items and exhibits from the scene.
Routes in and out of the search sites are meticulously planned as each deployment has to be performed in a way to ensure traces of the nerve agent are not inadvertently spread to other areas by those carrying out the searches.
Contingency plans are also put in place with specialist ambulance and fire and rescue teams put on standby to respond and support the search teams or in the event of any emergency health or hazard situations developing.
Once each deployment has been planned, protective equipment for each individual takes around 40 minutes to put on and is specifically selected depending on the activity and role they will be carrying out inside the scene.
This is done inside forensic tents to ensure the suits remain sterile before entering the crime scene, but with the recent hot weather, temperatures inside the tents have been reaching in excess of 40 degrees centigrade.
Once inside the scene, those carrying out the searches are limited to around 15-30 minutes working-time before they have to exit due to the effects of heat and exhaustion. The nature of the protective suits also means visibility and dexterity are also extremely limited; further hampering the searchers in their task.
Any exhibits or samples collected are carefully recovered and sent for testing at the Defence, Science and Technology Laboratory at Porton Down.
The scientists and forensic officers then begin the process of disrobing from the protective suits - which again takes around 40 minutes - to ensure they are not exposing themselves or any others to the risk of contamination.
Blood samples from everyone entering a scene are taken regularly and compared against a baseline sample to check for any signs of exposure to the nerve agent that they are working to find.
Typically, only two deployments per day can be carried out at any particular scene per day.
To date, more than 400 exhibits have been recovered as part of the Amesbury investigation, of which a significant number are potentially contaminated and have been submitted to DSTL labs for analysis. This includes the small bottle, which was recovered from the address in Muggleton Road and which detectives now believe to be source of the contamination of Charlie and Dawn.
Work is ongoing to establish whether the nerve agent is from the same batch as used in the attack against Sergei and Yulia Skripal in March, and this remains a main line of enquiry for the investigation team.