TED科学:Simona Francese: Your fingerprints reveal more than you think

Do you ever stop and think,during a romantic dinner,"I've just left my fingerprintsall over my wine glass."


Or do you ever worry,when you visit a friend,about leaving a little piece of you behindon every surface that you touch?And even this evening,have you paid any attentionto sit without touching anything?Well, you're not alone.Thankfully, criminals underestimatethe power of fingerprints, too.And I'm not just talking aboutthe twisted parting of linesthat make our fingerprint unique.I'm talking aboutan entire world of informationhiding in a small, often invisible thing.In fact, fingerprintsare made up of moleculesthat belong to three classes:sweat molecules that we all producein very different amounts ...molecules that we introduce into our bodyand then we sweat outand molecules that we may contaminateour fingertips withwhen we come across substanceslike blood, paint, grease,but also invisible substances.And molecules arethe storytellers of who we areand what we've been up to.We just need to havethe right technology to make them talk.

So let me take you on a journeyof unthinkable capabilities.Katie has been rapedand her lifeless body has been foundin the woods three days later,after her disappearance.The police is targeting three suspects,having narrowed downthe search from over 20 menwho had been seenin that area on the same day.The only piece of evidenceis two very faint,overlapping fingerprintson the tape that was foundwrapped around Katie's neck.Often, faint and overlapping fingerprintscannot help the policeto make an identification.And until recently,this might have been the end of the road,but this is wherewe can make the difference.

The tape is sent to our labs,where we're asked to useour cutting-edge technologyto help with the investigation.And here, we use an existing formof mass spectrometry imaging technologythat we have further developed and adaptedspecifically for the molecular and imaginganalysis of fingerprints.In essence, we firea UV laser at the print,and we cause the desorptionof the molecules from the print,ready to be capturedby the mass spectrometer.Mass spectrometry measuresthe weight of the molecules —or as we say, the mass —and those numbers that you see there,they indicate that mass.But more crucially,they indicate who those molecules are —whether I'm seeing paracetamolor something more sinister,forensically speaking.

We applied this technologyto the evidence that we haveand we found the presenceof condom lubricants.In fact, we've developed protocolsthat enable us to even suggestwhat brand of condom might have been used.So we pass this information to the police,who, meanwhile,have obtained a search warrantand they found the same brandof condom in Dalton's premises.And with Dalton and Thomsonalso having records for sexual assaults,then it is Chapman that may becomethe less likely suspect.But is this informationenough to make an arrest?Of course not,and we are asked to delve deeperwith our investigation.

So we found out, also, the presenceof other two very interesting molecules.One is an antidepressant,and one is a very special molecule.It only forms in your bodyif you drink alcoholand consume cocaine at the same time.And alcohol is known to potentiatethe effects of cocaine,so here, we now have a hinton the state of mindof the individualwhilst perpetrating the crime.We passed this information to the police,and they found out that, actually,Thomson is a drug addict,and he also has a medical recordfor psychotic episodes,for which presumablythe antidepressant was prescribed.So now Thomson becomesthe more likely suspect.But the reality is that I still don't knowwhere these molecules are coming from,from which fingerprint,and who those two fingerprints belong to.

Fear not.Mass spectrometry imagingcan help us further.In fact, the technology is so powerfulthat we can see wherethese molecules are on a fingerprint.Like you see in this video,every single one of those peakscorresponds to a mass,every mass to a molecule,and we can interrogate the software,by selecting each of those molecules,as to where they are presenton a fingermark.And some images are not very revealing,some are better,some are really good.And we can create multiple imagesof the same mark —in theory, hundreds of imagesof the same fingerprint —for as many of the moleculesthat we have detected.

So step one ...for overlapping fingerprints, chances are,especially if they comefrom different individuals,that the molecular compositionis not identical,so let's ask the softwareto visualize those unique moleculesjust present in one fingermarkand not in the other one.By doing so,that's how we can separatethe two ridge patterns.And this is really importantbecause the police now are ableto identify one of the two fingerprints,which actually corresponds to Katie.And they've been able to say sobecause they've comparedthe two separate imageswith one taken posthumously from Katie.So now, we can concentrateon one fingerprint only —that of the killer's.

So then, step two ...where are these threemolecules that I've seen?Well, let's interrogate the software —show me where they are.And by doing this,only portions of the imageof the killer's fingerprint show up.In other words,those substances are only presentin the killer's print.So now our molecular findingsstart matching very nicelythe police intelligence about Thomson,should that fingerprint belong to him.But the reality is that that printis still not good enoughto make an identification.

Step three:since we can generate hundreds of imagesof the same fingerprint,why don't we superimpose them,and by doing so,try to improve the rich patternof continuity and clarity?

That's the result.Striking.We now have a very clear imageof the fingerprintand the police can run itthrough the database.The match comes out to Thomson.Thomson is our killer.


Katie, the suspects and the circumstancesof the crime aren't real,but the story contains elementsof the real police caseworkwe've been confronted with,and is a composite of the intelligencethat we can provide —that we have been ableto provide the police.And I'm really, really thrilledthat after nine years of intense research,as of 2017,we are able to contributeto police investigations.

Mine is no longer a dream;it's a goal.We're going to do this wider and wider,bigger and bigger,and we're going to knowmore about the suspect,and we're going to build an identikit.I believe this is also a new erafor criminal profiling.The work of the criminologistdraws on the expert recognitionof behavioral patternsthat have been observed beforeto belong to a certain type,to a certain profile.As opposed to this expertbut subjective evaluation,we're trying to do the same thing,but from the molecular makeupof the fingerprint,and the two can work together.

I did say that molecules are storytellers,so information on your health,your actions, your lifestyle,your routines,they're all there,accessible in a fingerprint.And molecules arethe storytellers of our secretsin just a touch.

Thank you.

(Audience) Wow.


来自:VOA英语网 文章地址: http://www.tingvoa.com/html/20181012/Simona-Francese-Your-fingerprints-reveal-more-than-you-think.html