When the Falkland Islands Police reopened the investigation into the disappearance of Marine Alan Addis, they didn't know where to start.
The Islands stretch for 4,700 square miles – roughly the size of Wales – in a jumble of rocks, reefs and peat bogs.
Officers had new leads to follow but knew that such a vast territory would be difficult to search with limited resources.
So in 1997, a specialist team set up to assist authorities in locating human remains travelled from the UK. It included an expert in forensic archaeology, ground penetrating radar and a specially trained sniffer dog, Lee.
Mick Swindells, its handler, was given a Home Office Research Award to study the training and use of cadaver detection dogs in 1996 and trained also Army officers in this speciality.
As well as the Addis case, he was involved in the search of missing five-year-old Rosie McCann.
The girl had vanished from her home and after looking for her for seven weeks, police were stuck.
However, Mick Swindells found her in only a few hours.
These dogs have been used in many other investigations, such as the Moor Murders and to locate the remains of those buried in secret after the Troubles in Northern Ireland.
How do they operate?
Cadaver detection dogs can be used to detect human remains in a variety of circumstances, whether they are buried as a result of crime or natural disasters, concealed on the surface or submerged in water.
They are trained to discriminate between the 'target scent' and other similar innocent smells, eliminating “false positive” indications.
When they pick up the scent of a recently deceased, putrefying or skeletonised human corpse, they will signal to their handler who will then identify the area of interest.
Furthermore, dogs are able to search an area three-dimensionally by using their sense of smell, while humans can only look two-dimensionally, or in line of sight.
Mick Swindells says the reason dogs are used is that their sense of smell is much better than humans: "Their olfactory system is about 350 times better than ours.
"It's likened that a dog could detect a bottle of whisky in Lake Windermere, that's how good a dog nasal system is."
In perspective, the nose of a German shepherd contains about 220 million olfactory cells, while a human nose has about 20 million.
For these reasons, the use of these dogs enables authorities to search large areas in a quicker and more effective way than with other techniques.
After the Lockerbie Air Crash in 1988, 50 dogs were used to search 860sq miles and helped locate bodies, personal effects and clues for the investigation.
But techniques have developed since then.
Mick Swindells has trained the first Forensic Marker Detection dogs in the world in this field.
The dog is able to detect different forensic security markers - or synthetic DNA - on all conceivable surfaces, such as metal, stone and plastics.
This can be useful to identify a person's remains as well as objects.
Ronnie the Labrador is the second to be able to do so:
How are they trained?
As human remains are not allowed to be used in training in the UK, pig flesh is used instead.
Pigs have similar anatomical characteristics to humans and are both omnivores.
However, the key to training a search dog is the ball. Swindells said: "We use this desire for the ball to teach the dog to find drugs, explosives, forensic markers, anything.
"And the main thing is that the dog is enjoying it and wants to do it. You can't force a dog to do anything.
"Because these dogs have such a high drive, they'll work all day and all they want is the ball."
What are their limitations?
Unlike other search techniques, dogs are sentient beings and are able to recognise a corpse across a range of environmental conditions.
"The best thing about using a dog to detect cadavers, as opposed to machines, is that dogs have the ability to think. But that's also the worst thing about using dogs."
In fact, canines can be tricked by a series of environmental circumstances, such as peat bogs, which produce methane, a chemical compound, in the same way as corpses do.
Furthermore, dogs work operationally and their success rate can only be assessed in training. Swindells explained: "Nobody has ever said 'you missed the DNA or drugs, it's over here!' The only exception is explosives, when the big bang will let you know you missed it.
In the case of Jazz and Ronnie, Swindells had to judge if there was any 'innocent' substance which would give a false positive during training: "So far we have not come across anything," he said, "Therefore the 'success rate' for the dogs is 100%."
In other circumstances, the location of the search might constitute the biggest problem.
For example, for the case of Alan Addis in the Falklands, the expanse of the area to be searched and the lack of meaningful intelligence to give us a precise scenario was crucial for the search.
"We had to 'guess' the areas - of which there were many," Swindells said, "We then had to determine how intensely to search each area given our time schedule and amount of land to be searched."