Criminals Learn Forensic Science

Criminals are adapting to advances in forensic science:

There is an increasing trend for criminals to use plastic gloves during break-ins and condoms during rapes to avoid leaving their DNA at the scene. Dostie describes a murder case in which the assailant tried to wash away his DNA using shampoo. Police in Manchester in the UK say that car thieves there have started to dump cigarette butts from bins in stolen cars before they abandon them. “Suddenly the police have 20 potential people in the car,” says Rutty.

The article also talks about forensic-science television shows changing the expectations of jurors.

“Jurors who watch CSI believe that those scenarios, where forensic scientists are always right, are what really happens,” says Peter Bull, a forensic sedimentologist at the University of Oxford. It means that in court, juries are not impressed with evidence presented in cautious scientific terms.

Detective sergeant Paul Dostie, of Mammoth Lakes Police Department, California, found the same thing when he conducted a straw poll of forensic investigators and prosecutors. “They all agree that jurors expect more because of CSI shows,” he says. And the “CSI effect” goes beyond juries, says Jim Fraser, director of the Centre for Forensic Science at the University of Strathclyde, UK. “Oversimplification of interpretations on CSI has led to false expectations, especially about the speed of delivery of forensic evidence,” he says.

Posted on September 9, 2005 at 7:16 AM36 Comments


Unixronin September 9, 2005 7:44 AM

I believe the Law of Unintended Consequences applies in spades. Portray forensic investigators on TV as detective geniuses of the caliber of Sherlock Holmes, and it was only a matter of time before the uneducated, easily-influenced TV-watching masses that lawyers prefer as jurors started throwing out cases because the forensic investigators weren’t Sherlock Holmes.

I suspect this would be much less of a problem if lawyers weren’t so eager to dismiss every potential juror whom they think might be capable of objectively examining the evidence and making up their own mind. Several friends of mine who have been repeatedly called for jury duty, but rarely actually served on a jury, tell me that if you want to avoid being selected for any given case, just admit to having an engineering degree; the defense and prosecution attorneys will practically fall over themselves to drop you from the jury pool.

aetius September 9, 2005 7:59 AM

The comment about the sterile room and the volunteer is misleading. Of course it is easy to get the DNA for the one person who enters the sterile room — that’s the only evidence there. A more accurate test would be getting the DNA sample from one volunteer in a crowded police office area, with literally years of evidence piled up all around. The thieves using cigarette butts is more on track with what is actually happening — contaminating the site with evidence from so many people that it is impossible to pick out the suspect beyond a reasonable doubt. You can’t be totally clean, but you can hide in the crowd pretty easily.

Clive Robinson September 9, 2005 9:08 AM

The thing with cars is not new, nor is the idea of planting missleading clues for those that read things like Miss Marple and other detective stories.

In reality in the US it was known that on atleast one occasion a “Bum” was “rolled” to get their whisky bottle with their finger prints on it to plant as false evidence in a stolen car used for a “hit and run” murder. The Police either assumed it was a drunk driver or spent considerable time chasing the wrong person.

The police eventually found out about this bercause somebody boasted about it. Criminals appear incapbable of keeping their mouths closed, as something like 80% of solved crimes (in the UK) started with a tip off where somebody had talked…

In the UK a barister was struck off for advising (criminal) clients about how to evade “forensic” investigation, and how to throw a bad light on the results if they did find themselves in the dock. Somebody told a television reporter and the Barister was secretly filmed…

In reality this is a case of evolution on behalf of the criminal, it is simply a case of “turning the weapons against the attacker”. If they did not find out from television, then it would be via books the Internet or some other source of information.

If you realise that all technical solutions have weaknesses and problems this gives rise to the posability of exploting them. If you exploit them in the right way the technology becomes steadily less reliable / applicable untill it is finally not used / depreciated / discredited and usually replaced with a new piece of technology.

Think about people using poison as a murder weapon, historicaly arsnic was favourate untill a reliable test came along, now few people would use it as a weapon. So the test has become depreciated, unless there are other reasons to perform it. SO technicaly savey poiserners have used medical science to find other (almost) unditectable poisons to use instead (think of Giorgy Markov and ricin). In fact a search on the internet might be helpful 😉

With regards other evidence if you think back to “Gummy Fingers” that Bruce had in Cryptogram and later in his blog, it becomes obvious that making false evidence is actually not that difficult.

DNA evidence is likewise unreliable, if you used the same techniques to replicate a persons DNA as the forensic scientist uses to magnify a DNA sample up for testing, you can sufficiently contaminate the crime scean to show that persons DNA even if they where not there.

Dima September 9, 2005 9:29 AM

It’s right from those “movie plots” – condoms and latex gloves have been used by perps on “Law & Order” and the like for quite some time now.

Bruce Schneier September 9, 2005 9:38 AM

“The police eventually found out about this bercause somebody boasted about it. Criminals appear incapbable of keeping their mouths closed, as something like 80% of solved crimes (in the UK) started with a tip off where somebody had talked…”

I believe the stupidity of criminals is one of the most potent weapons we have in the war on crime.

Phil W September 9, 2005 9:53 AM

It seems highly surprising to me that this is anything new – criminals have (usually)worn gloves so as not to leave fingerprints. It seems unbelievable to me that they would not wear fully encompassing suits of plastic if they could (a) buy them without suspicion, (b) not be rather conspicious walking round, entering and exiting properties in them, and (c) dispose of them securely, so I’d have expected common plastic gloves and condoms to be standardly used; maybe my expectations are (fortunately) too high…

DarkFire September 9, 2005 10:28 AM


“I believe the stupidity of criminals is one of the most potent weapons we have in the war on crime.”

You wouldn’t believe how true this is…

Very fortunately the average criminal is totally stupid and is quite happy to leave all sorts of evidence behind at the scenes of their crimes. The intelligent criminals are much more of a challenge and Clive is correct when he states that most crimes are ultimately solved because someone talked.

Of course forensic science is a superb investigative and evidencial tool and can yield some truly astonishing results, but so many crimes are solved by
pure chance: a man pulled over because of a broken tail light, a cigarette end falling in just the right place, a scrap of clothing being caught on a nail, the list is endless.

Unfortunately still more crimes go unsolved because for example it failed to rain the night before, or the wind blows some leaves the wrong way etc. etc. Again the list is endless.

I would say that the majority of police work is plugging away at people, asking the right people the right questions until someone says something they shouldn’t have.

In a circuitous way this again goes back to the old people-vs-technology argument: many more crimes are solved by experienced detectives asking the right questions to the right people than are solved by the latest nuclear powered static discharge chrome plated DNA hoover tool!

As allways, my $0.02…

J.D. Abolins September 9, 2005 10:38 AM

A similar article on the “CSI Effect” a few months ago noted the ease of unwittingly providing more material for forensic examination when trying to use countermeasures. (I don’t remember where the article appeared.)

Example: A criminal hears about DNA being extracted from envelop gum. She he tries to use tape or self-adhesive envelops to avoid leaving DNA on a ransom note. The tape catches fingerprints, hairs, dust, etc.

Then there is the time factor. Technologies change and if an old case is reopened, evidences can reveal new clues.

Then there are the human factors, such as boasting that others already mentioned. Don’t forget careless and spiteful associates, family members, etc.

J.D. Abolins

albert b September 9, 2005 10:45 AM

In earlier posts, Bruce has suggested that when the government gets more power (from things like satellite images) to detect crimes (such as unpermitted home improvements) the penalties for said crimes should be diminished correspondingly.

If the penalties should be mitigated when government gains access to new technologies which increase its ability to gain evidence against criminals, should these penalties again be strengthened when knowledge of evading these technologies spreads to the criminal community?

havvok September 9, 2005 11:48 AM

@ albert b
Well, it makes sense that penalties are increased if a criminal is convicted; the beauty of applying countermeasures is that it provides a strong foundation when trying to prove pre-meditation.

Davi Ottenheimer September 9, 2005 11:57 AM

The evolution is a natural byproduct of awareness; we see a similar shift in digital forensics as well.

“jurors expect more because of CSI shows”

I love it when I see TV-plot security like the souped-up “digital-enhancement” that can zoom in and reconstruct just about anything you need to solve a crime. “Hey, look carefully, there’s the smoking gun!”

Many of these shows completely obliterate the fact that technology can not (yet) solve a case on its own, however, without a human performing crisp analysis of the accumulated data. Alas, for some reason smart investigators, ala Poirot or Holmes, are far less interesting today to the public than smart tools.

“80% of solved crimes (in the UK) started with a tip off where somebody had talked”

Indeed, and as long as you have sufficient tips and suspects, the technology advances do very little to avoid issues like the prisoner’s dilemma.

Davi Ottenheimer September 9, 2005 12:11 PM

“thieves there have started to dump cigarette butts from bins in stolen cars before they abandon them”

Well, as the old saying goes:
“When cigarettes are illegal, only criminals will smoke cigarettes”

David September 9, 2005 12:14 PM

DNA evidence is likewise unreliable, if you used the
same techniques to replicate a persons DNA as
the forensic scientist uses to magnify a DNA
sample up for testing, you can sufficiently
contaminate the crime scean to show that persons
DNA even if they where not there.

I question this. To my mind (and I may well be mistaken) most DNA tests are not performed on samples of DNA found strewn about, but rather on DNA extracted from something like hair, skin, semen, etc. To plant such evidence, one would have to actually be able to duplicate these vectors, rather than simply the DNA molecule itself.

Again, I’m not a forensic specialist, and could well be missing something…

george September 9, 2005 6:45 PM

And loonie liberal left-wing moonbats like you continue to believe in giving up secrets to the Bad Guys.

Why don’t you just accept the evidance and advocate full secrecy, with disclosure of any cryptographic or other sensitive material meritting an automatic charge of treason?

Davi Ottenheimer September 9, 2005 7:57 PM

Um, george, it’s really hard to tell who or what you are actually trying to insult, and even harder to fill in the gaps in your statement:

1) what evidence?

2) what gets defined as “sensitive material” and by whom?

3) really, you would treat disclosure of ANY cryptographic material as treason?

4) treason against what nation (see #2)?

Neighborcat September 10, 2005 6:18 AM

Bruce, “war on crime”?

There are apparently “wars ” on crime, drugs, poverty, terror, hunger, homelessness, teen pregnanacy, illiteracy, the common cold, Nathan Lane, Iraq, obesity, anorexia, greenhouse gases, black mold, and the heartbreak of psoriasis.

I am always taken aback when I hear someone I consider intelligent unthinkingly co-opt the language of our idiot ruling class.

I’m not just being peevish about semantics here, I’m genuinely concerned about the conceptual shortcuts and unconsidered implications that this encourages.

Example: War on Crime. If it’s war, its “Us” against “Them” and our side is the side of all that is good, “They” are flawed from their deepest moral foundation to their unwashed ears, and must be wiped out. No room for understanding, no room for compromise or introspection, this is war.

Criminals. Have any of us never broken a law? Whoops, now I’m on the wrong side.

Drugs. Never taken a drug? Oh wait, you meant an illegal drug. But wait, I can buy my amphetamines on the street, or from the pharmacy with a prescription. I’m confused.

Poverty. Jesus is reported to have said “The poor you will always have with you.”
This is usually misinterpretedd as a call to action, It’s not. Its a warning. If there is inequality, by definition someone has to be poor.

The solutions to all of these problems are in the details. We gloss them over at our own peril.

Yep, you’ve guessed it, I’ve declared war on sloppy language and fuzzy thinking.

rarabinks September 11, 2005 3:27 AM

Neighborcat, you and your Ivory tower dwelling leftist brethren are the only ones worrying about the semantics.

Just because you hear institutions and government give a catch-all phrase to describe a highly complex phenomenon doesn’t mean that the government and institutions forget that the reality is always more complex than can be described.

They give it a simple umbrella concept or metaphor to cover the myriad complex system for the purpose that people have a general idea about what phenomenon the government is talking about. Would you prefer that the government start naming these things in specific, situational terms with highly complex definitions (that really will never match the reality anyway) and have the system be even more inherently chaotic?

I suppose it wouldn’t matter anyway to you. Cause your ilk will always nitpick.

Neighborcat September 11, 2005 6:08 AM


Perhaps if you had not been so intent on crafting your ad hominem attack, you would not have missed my point so completely.

Language influences thought and vice versa. Generalizations and convenient catch-all phrases hide the complexity of issues. If you don’t have the time to deal with the details or investigate assumptions, why are you talking about an issue at all?

Davi Ottenheimer September 11, 2005 7:19 AM

@ rarabinks

“you and your Ivory tower…are the only ones worrying about the semantics”

If you’re not worried about the semantics, then why are you posting about it? If I had a dollar for every person that used completely self-defeating reasoning…

And what does this have to do with the log entry anyway? Are you trying to suggest that a “simple umbrella concept or metaphor to cover the myriad complex system” is somehow the opposite of Ivory tower thinking?

Here’s a good test case for your theory: forget the war on crime, howabout the “War on WMD”

“Would you prefer that the government start naming these things in specific, situational terms with highly complex definitions”

Personally, no. I’d just prefer more honest names. Colin Powell should never have been forced to lie about “proof” to the United Nations:

It might have been complex, but the real risk of WMD needed to be accurately understood instead of presented as a “simple umbrella” of fear.

rarabinks September 11, 2005 7:36 AM

Neighborcat, oh yes I get your point and I’m attacking the flaws in your “war on sloppy language and fuzzy thinking”. It seems you completely missed my argument.

Neighborcat, For whom does the catch-all phrases and generalizations hide the complexity of issues from? The citizenry, government, or some other actor?

Are you saying Government themselves are not aware of the complexity of issues? Are you judging the internal disposition of institutions?

Are you saying the Citizenry cannot get past the impenetrable fog of simplifying issues and make decisions themselves by indepedent investigation? Would you prefer the citizenry to be doused in information about complex systems?

rarabinks September 11, 2005 7:53 AM

Davi, in relation to your first question: I’m worried about it because his own supposed “war on sloppy language” is sloppy in itself. In relation to the second: Neighborcat was the one who started the issue in the first place I was merely responding. The third: No, where did I mention that? I was stating that sometimes institutions need to give out simplified information of complex issues for reasons such as time and so forth. It is up to the citizenry to investigate further into the complexity and make up their own mind.

In regards to your statement about WMD’s as being under the “simple umbrella of fear”. First of all it was one institution communicating to another institution so the ‘theory’, as you so eloquently put it, doesn’t hold in this case because I’m talking about institution-citizen interaction. Where did the the government mention fear in the case to the U.N about WMD’s in Iraq?

Davi Ottenheimer September 11, 2005 8:55 AM

“the case to the U.N about WMD’s in Iraq” was in itself one of the government’s attempts to foment fear and perhaps loathing as well in citizenry.

“It is up to the citizenry to investigate further into the complexity and make up their own mind.”

True, although that’s hard to imagine if Colin Powell himself said he was deluded and deceived by the intelligence community he depended on. At some point the citizenry has to be able to trust someone in government, rather than having to each individually actively validate, and re-validate every detail, or what’s the point of having an election?

Davi Ottenheimer September 11, 2005 8:57 AM

“‘war on sloppy language’ is sloppy in itself”

I have no idea what that is supposed to mean.

Wait, are you using sloppy language to make a point? Or am I just a sloppy reader?

rarabinks September 11, 2005 8:05 PM

Davi, again where did the U.S. promote fear as their primary purpose?

Please point out to me the exact causal flow of events that led from the supposed promotion of fear to the emotional contagion in the citizenry. And where are the quantitive & qualitative measurements of fear in the citizenry? Or are you basing this on conjecture and your interpretation?

“are you using sloppy language to make a point?”

No no. It’s pretty simple. Neighborcat said ” I’m genuinely concerned about the conceptual shortcuts and unconsidered implications that this encourages.” For some reason Neighborcat thinks his language, which he extrapolated through conceptual shortcuts in his examples, can somehow explain the complexity of the issues and that institutions cannot.

Not that any of this matters anyway because you chose to engage me on the WMD issue which I pointed out was institution to institution communcation not citizen-institution interaction. Feel free to cherry pick again.

Davi Ottenheimer September 11, 2005 9:35 PM

“where did the U.S. promote fear as their primary purpose”

What does that mean? Purpose for what? Are you asking if they had to convince peope to be afraid of WMD in Iraq?

“supposed promotion of fear to the emotional contagion in the citizenry”

Please, if you’re telling me that fear of WMD in Iraq was not used to justify the attack, then you have some catch-up reading to do. Seriously. Read Colin Powell’s statements, if you will. He says he was misled, he regrets his PUBLIC presentation as a “blot” on his career.

“institution to institution communcation not citizen-institution interaction”

This makes no sense at all. Are you saying a Secretary of State’s public presentation to the United Nations is not a form of communication with the citizens of the US?

That’s crazy. Take a look at this. Here is “the institution” communicating with you, “the citizen”; direct and in stereo, for your individual listening pleasure:

(Note the byline from the Whitehouse called “Denial and Deception” — I wonder if they should change that, given Powell’s recent revelations about how he felt decieved by the intelligence community)

Note that his presentation was not called US to UN communication, but “U.S. Secretary of State Colin Powell Addresses the U.N. Security Council.” In other words he was addressing the UN, for everyone to see/hear. That is the point of a public address, no?

By the way, I really liked the roll of your phrase “his language, which he extrapolated through conceptual shortcuts in his examples, can somehow explain the complexity of the issues and that institutions cannot”. It sounds great when I read it aloud, but I can’t figure out what it supposed to mean.

Neighborcat September 12, 2005 5:02 AM


To answer your questions from Sept 11th, 7:34am, by paragraph:

Paragraph 1, Yes,yes, and yes.

Paragraph 2, Yes, and yes.

Paragraph 3, Yes, and not only yes, but I think it is vital. Why do you so fear being informed about complex systems?

Clive Robinson September 12, 2005 7:30 AM

@Rob W

I would not like to steal the scientists credit, but a search in past blogs will show I actually described how to Clone DNA and contaminate a crime scean in some depth a while ago.

I also sent an Email to Bruce about it some time before that…

The odd thing is that I looked into it some time ago, and then went chatting to various people about it. The responses I had from some experts was that I was sugesting herrasy. However not one of them had done any investigation, nor where they going to…

So hats off to Dr David Berryman (DNA expert) from Murdoch University, he’s done the work that others “feared” to do, he deserves a lot of credit.

Ari Heikkinen September 13, 2005 3:59 PM

It’s a fact that most criminals are extremely stupid. Seems most, if not all, criminals don’t actually do any security evaluation comparing possible gains against possible penalties. Then some crimes are just plain silly. I mean, take rapes for instance, why would anyone plan raping someone (and plan ahead trying to avoid leaving evidence) when it would likely be easier to go and pick someone from a bar or go to streets and pick a hooker for a little fee if they’re that desperate. Go figure.

Clive Robinson September 13, 2005 7:31 PM

@Ari Heikkinen

If it was just sex then you would be right, however as I understand it Rape is often not about sex but power over another nearly helpless person.

A significant number of rapes are planed, and are carried out in a place the victim would normally feel safe in (ie their home). Sometimes the rapist brings ritulistic items with which to intimidate and torture the victim (it’s these that have in the past help catch the rapist).

Mike Graham September 13, 2005 8:41 PM

Criminal stupidiy is probably the second best weapon against crime. The first is the cop arrests someone, tells them to tell him/her something interesting and he might forget about this criminal. The criminal will almost always rat out someone else who has committed a bigger crime. Narco cops are particularly fond of this as you can always get some idiot you’ve arrested for possession to give up his dealer is this arrest sends him to prison. There is no longer honor among thieves.

MOrgan February 22, 2007 7:16 PM

i cant belive what this world is coming to. now we have criminals knowing how to fool the system. which is one of the scariest things i’ve ever had to think of!

nanzala wafula April 10, 2007 2:49 AM

The judicial system in most countries has contributed tramendously to what we term “criminals knowing how to fool the system”.

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