From soil analysis to plants being broken, all kinds of material can provide vital clues in criminal investigations. Here with topsoil experts Compost Direct, we look at some of the most intriguing methods of forensic investigation.

Getting to the root of it: plant-based forensics

Palynology, or pollen analysis, can prove vital to solving all sorts of crimes. Perhaps one of the most prolific cases in which palynology was used to help bring about a conviction was that of the Soham murders in 2002.

The Telegraph interviewed Professor Patricia Wiltshire regarding the case in which she provided crucial work. The bodies of Holly Wells and Jessica Chapman were found concealed in a ditch, with the foliage in the area appearing untouched. Upon inspection of the crime scene, Professor Wiltshire noticed that nearby stinging nettles had begun to produce sideshoots. Not only did this enable her to prove that someone had walked there — nettles only sprout in such a way when trampled underfoot — but the professor was able to say where the bodies had been taken to the ditch. She was also able to pinpoint a timeframe from the shoots by establishing when the nettles had been broken compared to the growth of new sideshoots.

Furthermore, the plant-reading professor proved that suspect Ian Huntley had been at the scene. By analysing the soil on his car and clothing, Professor Wiltshire was able to connect the soil from the car to the soil of the crime scene.

Cold case cards

Playing cards provide one way for inmates to pass their time behind bars. The faces of these cards are, therefore, seen by many different people from many walks of life. In order to tap into this wealth of potential information, police departments are selling playing cards with names, photos, and details of unsolved, cold cases to prison inmates. The process has been a success, with police in Connecticut  solving around 20 previously cold cases through tips from inmates who had seen information from the playing cards.

The initiative is being rolled out across the world following this success, with everywhere from Rhode Island to South Australia now adopting the policy too.

Convicted by a tree

When the body of Denise Johnson was discovered outside of Phoenix in 1992, the presence of a trucker’s pager nearby caused a large-scale search. The pager belonged to Mark Bogan, who claimed to have met Denise after she asked him for a lift. He claimed that after a series of altercations, she had left the truck and continued on foot. He hadn’t noticed until the next day that his pager was missing.

A medical examination showed that Denise had been strangled to death, but the case didn’t have much in the way of leads. The detective on the case decided to head back to the crime scene to check for more clues, and noticed a low-hanging branch on a nearby tree was freshly damaged. Taking a photo and some of the seeds from the tree proved vital to the investigation — though the truck was entirely clean of fingerprints, blood, or anything else that could implicate Bogan, there were two seeds from the same species of tree that the detective had found damaged at the scene.

The species of tree, however, is common all over the state of Arizona. Unless they could match the specific tree seeds found in Bogan’s truck with the tree at the crime scene, they had nothing. The technology didn’t exist at the time, so it took many months of experiments and personal funding from Dr Timothy Helentjaris, a plant molecular genetics specialist, to find that each tree had its own DNA profile. From this, the DNA of the tree seeds from the truck were matched to the damaged tree at the crime scene.