Sherlock Holmes is getting an upgrade.

While fingerprints and other clumsy clues are still immensely valuable for crime scene investigators, they now have so much more to work with.

The science of forensics is advancing at break-neck speed.

The tiniest tell-tales can now reveal all.

They can expose your diet, your habits, your state of mind - even your looks. And working behind it all will soon be powerful computer algorithms which can also warn of crimes before they are committed.

“When I watched those first series of CSI, I thought a lot of it was just rubbish,” says Professor Adrian Linacre, “but quite a lot of it is starting to come true”.

But, should it?

“I honestly think a lot of what we’re doing now is like Pandora’s box … we’re scientists, and we love to do things. Is it in the public interest? That’s another issue.”

FINGERPRINT OF LIFE

The swirls of skin that make up individual patterns for us all have been at the heart of criminal investigations for more than a century.

But fingerprints aren’t infallible. The stuff that produces the mark in the first place, however, may well be.

“If they leave behind a smudged print you couldn’t do anything with it,” Professor Linacre, a forensic science researcher at Flinders University, says. “Now you know there is DNA in that sample. The crucial part is to be able to take a sample from that to find out who touched the item.”

And it’s about more than just DNA.

We all carry other identifiable markers around with us in our daily lives.

Wherever a finger rests, it leaves behind a tiny smear of the fats, proteins – and bacteria – coating our skin.

The end result is a moving cloud of ‘us’. It’s called a microbiome.

And the microscopic traces it leaves behind can reveal an awful lot about who and what we are.

“That’s the thing for us in forensic science,” Professor Linacre says. “We’re looking at things you leave behind – and then building up a picture of you.

“That’s one thing we can do right now - build up a really neat picture of what you look like.”

MOLECULAR PHOTOFIT

DNA is becoming increasingly easy to find. But police don’t have everyone’s profile on file.

So they usually need something extra to isolate potential suspects.

Height. Weight. Physical features.

Witnesses and CCTV have long provided this kind of information, as has the analysis of tell-tales such as footprint size and impressions.

Soon, forensic scientists may be able to recreate a full-body ‘foto-fit’ of potential offenders from the tiniest DNA samples.

“Facial features, they’re all genetically based,” Professor Linacre says.

“Baldness ... there’s actually a gene for it. You can work that one out, and when it would have kicked in. Hair colour is an obvious one. People can change hair colours, but we’re very very efficient at determining true colours. Eye colour is also very efficient. But all of these, by the way, also tells us a lot about your ancestry as well.”

Even details such as your height and weight can be reconstructed from the detailed blueprints every cell in our body carries around.

“It’s building up a picture,” he adds. “It is building up little jigsaw puzzles and fitting them together - but you don’t have that box with a picture. What’s the best way to put them all together to try and build up that really neat picture? That’s what we’re doing.”

It’s called DNA phenotyping.

And while it’s not in use by crime investigators yet, it soon will be.

BACTERIAL WHISTLEBLOWERS

Our DNA is unique. Our fingerprints are unique. So are the colonies bacteria that live within and on us.

In fact, we carry more bacteria than human cells in our own bodies.

It is a colony continually being modified by what we eat, where we go and what we do. But it remains consistent enough for long enough to act as a clear marker of identity.

Wherever we linger, some of this bacteria shifts into the environment. The longer we stay somewhere, the larger the colony we leave behind.

And these can be unwitting witnesses.

Such is the power of our personal microbiomes that the potential exists to sample air from a crime scene, and determine who has been breathing it.

And, once again, while investigators may not have on file identifying whom a particular microbiome belongs to, it can tell them much about who that person is.

Our bacterial colonies are shaped by diet and drug use. But they also can indicate conditions such as irritable bowel syndrome and Parkinson’s disease.

It can also establish the existence of contact between individuals.

People and animals sharing a house – or workplace - also share their microbial communities. They’re passed about through shedding skin and touch.

When a family moves house, their microbiome moves with them – eventually edging out most traces of the previous occupants. When an individual leaves for a time, their contribution to the collective ‘cloud’ diminishes. Likewise, when a visitor stays for a while, they add their own distinctive ‘flavour’ to the mix.

These are all clues that can help substantiate – or refute – claims of alibi, or ignorance.

But your bacteria are not the only whistleblowers.

Scientists are now studying the trillions of viruses that make up an individual’s ‘virome’. As with a microbiome, these are likely to be in combinations unique to each of us.

METABOLITE BLABBERMOUTHS

Our tattle-tale bodies just won’t stop spilling the beans.

Our DNA and microbial colonies aren’t the only informants available to forensic scientists.

We literally are what we eat.

Our bloodstream distributes metabolites throughout the body. These are the nutrients digested by our stomachs, and processed through various bodily functions.

It’s a chain of processes science increasingly understands.

“We’re looking at metabolites because they reveal which genes have become active,” Professor Linacre says. “ Certain things which cause people to do things, like hormones, you can track: are they on or off?”

These metabolites end up on our skin. So, a simple touch can potentially reveal how much coffee you’ve been drinking, whether or not you eat enough greens – or regularly indulge in a whiskey or four.

“We call it epigenetics. For instance, is that person a smoker? You can do that. Is that person abusing alcohol? You can do that. Now, that doesn’t mean they’re committing crimes. But you can start to build up a much bigger picture of that person.”

And, unlike microbiomes, your personal metabolites can be vastly different from even those people you live closest to.

“The alcohol dehydrogenase gene is one very dear to my heart,” Professor Linacre quips. “It helps us process alcohol. I’ve probably got a double dosage - I’m from Glasgow originally … But it’s only prevalent in Western populations. Lactose (cow’s milk) tolerance. That’s another one. You can do a battery of these tests.”

A metabolite profile is unlikely to be enough for a conviction. But it will help build up a profile that strengthens the case against a suspect.

EXPOSOME SQUEALERS

The enormity of chemicals, microbes, fungi – along with the microbiome, metabolites and DNA – following us around is called an exposome.

It’s what we’ve been exposed to at home, work and play – as well as in transport, those we meet and where we’ve been.

Everything from pets and pollens through to perfume and cleaning agents clings to our bodies. And where we go, they go too.

“No one really knows how vast the human exposome is or what kinds of things are in there,” professor and chair of genetics at Stanford University Michael Snyder says.

What he knows is that there is a lot of it. And it’s different for everyone.

“It turns out, even at very close distances, we have very different exposure profiles or ‘signatures’,” Snyder says.

Researchers have long been able to detect the residue of drugs, explosives and smoke. Now, they can go so far as to determine whether your fingers had recently touched a condom – and what brand it was.

ARE YOU A ‘SHEDDER’?

The amounts of DNA needed to produce useful results are becoming ever smaller. Amplification techniques can work on even a few cells.

And while detectives can pick up microscopic samples at crime scenes, what isn’t so easy is determining how they got there.

For example: merely shaking somebody’s hand will almost inevitably result in an exchange of materials. So, when they later touch a doorknob, some of your DNA could be deposited there.

Determining whether or not a trace is reliable is a challenge addressed by Professor Linacre and his team at Flinders University.

One way of doing this is measuring how much DNA any given person sheds.

“We know that some people pass on more of their DNA because when they touch something more of their cells are left behind,” he says. “They are called shedders. “

He and his team have developed a simple test which reveals in a matter of minutes how much DNA an individual sheds. This helps indicate who was most likely to have last touched an item – and therefore link them to a crime.

The research also found men ‘shed’ more than women, and that thumbs leave behind the best DNA samples.

Professor Linacre says that the science behind such new forensic tests is good, and getting better. But the smaller the samples recovered, the greater the need for caution – and rigorous processes.

DNA carrying cells and biome samples can travel easily, through an innocent shake of the hand or merely sharing a pen. Not to mention doorknobs.

“We are aware of all of those things,” Professor Linacre says. “So, again, the science is right … but how do we think about that science? How do we interpret it? And how do we present that to courts? Small amounts of DNA does not implicate guilt.”

PRE-CRIME POLICING

Criminals are creatures of habit. Just like we all are.

And habits make us predictable.

The crime hasn’t been committed. But it’s about to be. Now smart computer algorithms can piece together clues to predict when.

Converting crime records into data to map-out the likelihood of future offences is nothing new. The US PredPol system sifts records of the timing and locations of crimes – such as burglary – to alert enforcers to patterns of behaviour. Police are then assigned in anticipation.

But that was just a start.

Now, enforcers can detect intent.

Just as we leave something of ourselves behind in everything we touch, our brain can imprint traces of our thought processes in everything we write.

It’s all about association.

EXPLORE MORE: Now AI can unravel the fingerprints of our mind

When we’re angry, happy or sad – different parts of our mind flare-up with activity. This, in turn, makes different sets of memories and perceptions more accessible.

It goes so far as influencing our choice of words, and the way we say it.

And each set of mental associations are individual: based on our own personal experiences, education and states of health.

David Kernot from Australia’s Defence Science and Technology Group has created algorithms that can establish the ‘fingerprint’ of our minds from just a few thousand words.

“If we’re stressed, that choice narrows as our brain is focused on other things. If we’re depressed, we focus on words grounded in reality. If we’re angry, imagery imprinted when we were in that state in the past will leap to the forefront of our minds the fastest.”

Because of this, a piece of writing – be it a tweet or treatise – can reveal much about the writer’s identity. Age. Education. Emotion. Mental health. Even intentions.

Kernot hopes this technology will soon be able to identify ‘lone-wolf’ suicide attackers – among others.

“You can see their anger increase,” he says. “You can see all this build up in their writing. It’s quite clear. You can actually see a shift prior to attacks. It’s feasible that this is an early warning signal for radicalisation. It’s possible. That’s really exciting.”

PANDORA’S BOX

“There’s a lot happening out there and the science is excellent. But … do we want to do this?” Professor Linacre asks.

Is extracting such immensely personal details from DNA necessary? What are the pitfalls?

Commercially available DNA ancestry tests are to be avoided, he says, both for their quality and potential unexpected uses.

“They’re rubbish … I tell people never do that. We don’t know what markers or bits of DNA they’re using, they’re not published in the public domain.”

Professor Linacre points to the recent Golden State serial killer and rapist case in the United States. Undercover FBI agents posed as someone wanting their ancestry tested, and actually sent in DNA samples collected at the crime scenes. One firm unwittingly revealed they had a close match on file - a cousin living in San Francisco.

“So then (the FBI) could say hold on, okay, we can start to look at all of their relatives. Did any fit all the other forensic profile details they’d assembled? They ultimately found the guy pretty quick.”

The cousin protested at the use of his personal data in such an unanticipated way. But it was pointed out that, there in the fine print above his signature, was notification his data could be shared with law enforcement agencies.

“I think the public should be completely aware of what’s happening and if you sign up to these things, well fine.- but note, this is what’s going to happen to your personal data,” Professor Linacre says.

At the moment, the testing necessary to build up an extensive DNA, microbiome, metabolite and exposome profile is expensive and time-consuming.

“A single test can take up to six hours. And they must be done individually,” Professor Linacre says.

But that’s all about to change.

“Give us three to five years, they will be done at the same time. All of those tests. In one simple reaction. And that will be a big breakthrough.”

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