How Scientific Is Forensic Science?

How Scientific Is Forensic Science? January 12, 2018

Forensics

Forensic science, as used by investigators on police shows and lawyers in the movies, is embedded in our cultural imagination as a reliable and objective instrument for establishing guilt and innocence. However, it appears that we’re idealizing forensics, which rely much more on subjective interpretations and questionable analyses than we’ve been led to believe. Law enforcement is guilty of overstating the reliability of forensic techniques, and scientific rigor is lacking in investigations.

Guilty Until Proven Guilty

Public Radio International’s podcast Science Friday cast doubt upon the scientific worth of tests that the criminal justice system has touted as ironclad for decades. The National Academies of Sciences, Engineering, and Medicine has criticized the procedures, and the FBI admits that its use of forensic techniques is geared to serve the prosecution in the majority of cases. In the podcast, the host talked to skeptics like Suzanne Bell, professor of forensic and analytical chemistry at West Virginia University:

IRA FLATOW: Let’s talk about a general lack of science in some big areas of forensic science. Let’s go through some of these– for example, like bite marks. How good are bite marks, Dr. Bell, for evidence?

SUZANNE BELL: Well, I think they’ve been pretty well discredited to this point. The science or the underlying assumptions of bite-mark analysis was that A, human dentition is unique, and B, that when you make those marks in skin, the skin will reflect that uniqueness. And both of those have been pretty well disproven. It’s a subjective method.

What’s worse, the much-needed oversight process is in limbo because the multidisciplinary commission President Obama appointed to oversee the reliability of forensic science —the National Commission on Forensic Science— is now gone because the Trump administration let the commission expire.

Class and Punishment

There are many aspects to this issue, not only scientific ones. The guests on the podcast talk about the way forensics disadvantages low income defendants, who don’t have the resources or know-how to challenge law enforcement analyses of crime scene data. Judges are hesitant to allow experts to testify against the state’s evidence unless they know why there should be a question raised about it, which in turn is unlikely without the expert testimony itself. The socioeconomic consequences of over-reliance on faulty forensics and exaggerated expert testimony are too significant to ignore.

State’s Evidence

The podcast doesn’t mention the point that is most glaring here, which is our cultural idea that evidence is objective and sacrosanct. The National Academy of Science was cautious about causing alarm in its report linked above, but it described a situation where the variations in methods, rigor, and training in the various disciplines that make up forensic science make it impossible to portray the process of identifying the guilty as in any way precise or objective.

Like any other science, forensics is about inference, not evidence. We need to acknowledge that data can be interpreted in many different ways, that we should question our certainty about the assumptions underlying these supposedly airtight methods, and that science is a legitimating institution that serves to protect the powerful and validate their authority.

I highly recommend people listen to the 18-minute podcast for an inside look at forensics and justice.

Do we put too much emphasis on the reliability and objectivity of forensic methods? 

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  • Do we put too much emphasis on the reliability and objectivity of forensic methods?

    It is unclear we have a superior option available, and emphases in other areas to compensate for the shortcomings of forensics, such as eyewitness testimony, are likely to be counterproductive as those methods of reporting are even more error-prone. If we grant that sometimes people commit crimes and that when they do there is a strong social interest for these rule-breakers to be caught and sanctioned, then we have to work with the tools available even while knowing that their truth-bearing qualities are defeasible. So, if the question is should we be perpetually unsatisfied with the state of forensic techniques and continue to improve them to make them less error-prone, then obviously yes. But meanwhile, the system that does exist is predicated upon a certain level of trust of the tools that already exist, and if there is a mismatch between the level of trust and the amount of trust that is actually warranted, the gap exists only because we have nothing better with which to close it.

  • Robert Baden

    One of the Innocence Project’s clients, who was convicted on bite mark evidence, and was cleared by DNA evidence, has made it his mission to challenge bite mark evidence whereever it is being used.

  • Robert Baden

    If a technique is not better than a coin toss it shouldn’t be used, no matter how much trust people put in it.
    Texas may have murdered an innocent because of questionable forensic evidence about how a fire started.

  • Texas may have murdered an innocent because of questionable forensic evidence about how a fire started.

    We’ve been talking about that on this channel a lot. That was the one where the kids died in the fire, and it was supposed that the father started the blaze as some sort of Satanic pentagram of death. Later on, investigators realized that the open windows that fed the fire only made the burn pattern appear star-shaped.

    It certainly suggests that forensic techniques make investigators overconfident that they’re not just seeing what they want to see.

  • Jim Jones

    Far too often the “scientific evidence” used at trial is about as valid as palm reading or psychic visions. “Hair analysis” and “bullet lead analysis”, both used by the FBI, turned out to be bullshit.

  • Neko

    Apologies for spamming, but this New Yorker article on the Willingham case in Texas is excellent. However, one of the heroes of the story, scientist and arson investigator Dr. Gerald Hurst, complained that the problem with arson investigation was that it wasn’t scientific enough.

    “People investigated fire largely with a flat-earth approach,” Hurst told me. “It looks like arson—therefore, it’s arson.” He went on, “My view is you have to have a scientific basis. Otherwise, it’s no different than witch-hunting.”

    https://www.newyorker.com/magazine/2009/09/07/trial-by-fire

  • It’s an open secret in the USA that most convictions are obtained through skin color analysis.

  • Gary Whittenberger

    SUZANNE BELL: Well, I think they’ve [bite marks] been pretty well discredited to this point. The science or the underlying assumptions of bite-mark analysis was that A, human dentition is unique, and B, that when you make those marks in skin, the skin will reflect that uniqueness. And both of those have been pretty well disproven. It’s a subjective method.

    GW1: Human dentition does not have to be unique for bite marks to be useful. They can rule out some suspects.

    STP1: The guests on the podcast talk about the way forensics disadvantages low income defendants, who don’t have the resources or know-how to challenge law enforcement analyses of crime scene data.

    GW1: Low income defendants will be appointed an attorney if they cannot afford one. This attorney always has the opportunity to challenge evidence and forensic science itself.

    STP1: The National Academy of Science was cautious about causing alarm in its report linked above, but it described a situation where the variations in methods, rigor, and training in the various disciplines that make up forensic science make it impossible to portray the process of identifying the guilty as in any way precise or objective.

    GW1: “Make it impossible to portray the process of identifying the guilty as in any way precise or objective”? “Impossible?” “In any way?” I think you are probably distorting and exaggerating the conclusions of the Academy. Present some quotes, citations, and links which support your summary.

    STP1: Like any other science, forensics is about inference, not evidence.

    GW1: Nonsense! Forensics is about evidence and inference. It is also about the basic science and training.

    STP1: We need to acknowledge that data can be interpreted in many different ways, that we should question our certainty about the assumptions underlying these supposedly airtight methods, and that science is a legitimating institution that serves to protect the powerful and validate their authority.

    GW1: This is more nonsense! Some data can only be interpreted in one way. Furthermore the number of ways a set of data can be interpreted varies from one to few to several to many. There are margins of error for different kinds of data and different sets of data of one kind. Forensic scientists rarely speak of “airtight methods.” That is your straw man. Science has no interest in protecting the powerful; that is irrelevant to science. Your postmodernism is showing.

    GW1: While forensic science needs to be improved, you have vastly overplayed your hand.

  • Gary Whittenberger

    I think you are exaggerating. These kinds of evidence are not conclusive, but often helpful. They often contribute to a cumulative case pointing to guilty or not guilty.

    It is true that some people expect too much out of them, but this need not be the case.

  • Gary Whittenberger

    In Florida, some of the evidence presented against Ted Bundy was bite mark evidence. He was executed. Do you think he was not guilty? Do you think the bite mark evidence was totally unhelpful?

  • Gary Whittenberger

    That you for your rational way of thinking about this. Juries should be presented with information about the reliability and validity of different kinds of evidence.

    A piece of evidence may not be conclusive, but may be like a part of a puzzle.

  • Gary Whittenberger

    I seriously doubt that the courts currently use any technique that is no better than a coin toss. If you think so, please tell us what that technique is and present evidence, citations, and links to support your claim.

  • Gary Whittenberger

    Of course there are going to be false positives and false negatives! Forensic science has the duty to improve and reduce these types of errors.

  • This is more nonsense!

    Gary says so!

  • Gary Whittenberger

    Shem says “Forensics is about inference, not evidence” and he knows so much about forensics.

  • Jim Jones

    Too many people trust the guy in the white coat. Read “RIGOR MORTIS” by Richard Harris for related information.

    > They often contribute to a cumulative case

    That’s the wrong way to judge a case.

    http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.557.9512&rep=rep1&type=pdf

  • safetynet2razorwire

    Science is obsessive in its ceaseless drive for ever-greater certitude.
    Forensic science need only pass the crude test of ‘reasonable doubt’.
    To jurors DNA is outweighed by “If the glove don’t fit you must acquit”.

  • Forensic science need only pass the crude test of ‘reasonable doubt’.

    That was the point of the article in the OP, though: judges and jurors aren’t scientists, and they’re usually not aware of the shortcomings of forensic techniques. Defendants are at a disadvantage because they’re being incriminated by methods that society thinks are much more objective and foolproof than they are.

  • Gary Whittenberger

    I disagree. In the US today not enough people trust the guy in the white coat. Also, no piece of evidence by itself may lead one to confidently conclude that a person committed a crime, but many pieces of evidence may do so. That is an appropriate way to judge a case.

  • We’re not just talking about false positives and false negatives. It’s the entire matter of forensics as a discipline. Society seems to think forensic methods are accurate and objective to an extent that their real-life practice isn’t; there’s still a lot of inference and interpretation involved, particularly in the context of a criminal investigation and trial. The researchers themselves may have an inflated sense of their own capabilities and expertise. Judges and juries may be unclear on how reliable forensic methods are, and as a result defendants could have a hard time demonstrating the need for experts to assess the forensic case on behalf of the defense.

    It’s a lot more complicated than just improving the reliability of the methods, and having faith that they’re being applied fairly.

  • Gary Whittenberger

    SP1: We’re not just talking about false positives and false negatives. It’s the entire matter of forensics as a discipline. Society seems to think forensic methods are accurate and objective to an extent that their real-life practice isn’t; there’s still a lot of inference and interpretation involved, particularly in the context of a criminal investigation and trial.

    GW1: I agree that it is important to educate the public, but especially jurors, on the accuracy and objectivity of forensic methods. But you should be careful not to throw the baby out with the bathwater. Forensic methods are still quite valuable in seeking the truth about the guilty and the not guilty.

    SP1: The researchers themselves may have an inflated sense of their own capabilities and expertise. Judges and juries may be unclear on how reliable forensic methods are, and as a result defendants could have a hard time demonstrating the need for experts to assess the forensic case on behalf of the defense.

    GW1: Ok, we agree that education is needed. Defendants don’t need to do what you say here. Their attorneys will or should do it for them. Miranda rights always mention the right to an attorney. This is standard in the US today.

    SP1: It’s a lot more complicated than just improving the reliability of the methods, and having faith that they’re being applied fairly.

    GW1: Reason, not faith, is required. But the most important task is to improve the reliability and validity of the methods. Education is secondary and can be done for jurors before or during the trial.

  • Let’s at least get straight what I’m not saying here. I’m not saying forensic methods aren’t valuable or should be thrown out, I’m saying we need to create a more realistic cultural outlook toward them.

    I’m not saying that defendants don’t or shouldn’t have attorneys, I’m saying that a judge is unlikely to allow experts to present testimony against the state’s evidence if the judge doesn’t understand the basis of the expert’s objection.

    And I’m not saying we shouldn’t try to improve forensic methods, I simply disagree that “the most important task is to improve the reliability and validity of the methods.” As I pointed out in the OP, it’s crucial to acknowledge that these methods are not as reliable and objective as the general public has been led to believe.

  • Gary Whittenberger

    SP2: Let’s at least get straight what I’m not saying here. I’m not saying forensic methods aren’t valuable or should be thrown out, I’m saying we need to create a more realistic cultural outlook toward them.

    GW2: IMHO, your essay presents an exaggerated negative view of forensic methods. I commented on the specific claims which I thought were problematic.

    SP2: I’m not saying that defendants don’t or shouldn’t have attorneys, I’m saying that a judge is unlikely to allow experts to present testimony against the state’s evidence if the judge doesn’t understand the basis of the expert’s objection.

    GW2: You appear to be just saying that some judges are not well educated. Well, yes, that would be the case. But most of them are well educated, understand the limits of forensic methods, and/or are willing to allow expert testimony on the methods in court.

    SP2: And I’m not saying we shouldn’t try to improve forensic methods, I simply disagree that “the most important task is to improve the reliability and validity of the methods.”

    GW2: Yes, we disagree on this point. The most important task is to discover the truth. The better the forensic methods, the more likely the truth is to be discovered. So I stand by my claim.

    SP2: As I pointed out in the OP, it’s crucial to acknowledge that these methods are not as reliable and objective as the general public has been led to believe.

    GW2: Crucial for what? It is not crucial for discovering the truth within a particular case in trial. Misconceptions can be and are corrected both before and during trials. You seem to be obsessed with a secondary problem whose correction would be helpful, but is not crucial, as you seem to think.

  • As per usual, we get to the point where you’re simply making assertions that are supposed to carry weight because Gary is making them. Forget what professors of forensics and analytical chemistry say, forget what a comprehensive study by the National Academies of Sciences, Engineering, and Medicine says, Gary says that I’ve exaggerated the negative aspects of forensics; judges are mostly really well educated in forensics and open to challenges to states’ evidence; and whether the general public understands the shortcomings of forensic methods is merely a secondary problem.

  • Gary Whittenberger

    SP3: As per usual, we get to the point where you’re simply making assertions that are supposed to carry weight because Gary is making them.

    GW3: As per usual, we get to the point where Shem simply glosses over the specific assertions I made and thinks hand waving is a defense.

    SP3: Forget what professors of forensics and analytical chemistry say, forget what a comprehensive study by the National Academies of Sciences, Engineering, and Medicine says, Gary says that I’ve exaggerated the negative aspects of forensics;

    GW3: You haven’t supported your claims with sound evidence. You provide no quotes, citations, or links to statements by any of these sources. You just interpret them and expect us to believe you. I am very skeptical of your interpretations. IMHO, your essay is poorly written.

    SP3: judges are mostly really well educated in forensics and open to challenges to states’ evidence;

    GW3: Yes, most judges are mostly well educated in this area. They all have gone to law school. They get continuing education. They get educated in the courtroom by expert witnesses. They read on their own. Sure, you’re going to find some judges who are not, but this is not most.

    SP3: and whether the general public understands the shortcomings of forensic methods is merely a secondary problem.

    GW3: Yes, it is a secondary problem, not a primary problem as you think. Judges and attorneys have an ethical obligation to educate juries in relevant forensic methods during the trial to correct any misconceptions they may have gleaned outside the courtroom.

    GW3: You just overplayed your hand, again.

  • You provide no quotes, citations, or links to statements by any of these sources.

    Sure I did, in the OP. There’s a link to the transcript of a podcast where the host interviews a professor of forensic and analytical chemistry; there’s a link to a comprehensive study by the NAS of issues in the field of forensics.

    Rather than toss around more accusations and insults, why not take a 24-hour breather from this blog and study the sources I cited? I insist.

  • Gary Whittenberger

    Ok, I withdraw part of my criticism — you did provide two relevant links, but you provided no quotes of experts or the actual researchers to back up your claims. In the case of bite mark evidence, you failed to tell us the exact level of accuracy for this and how the accuracy was determined by scientific research.

    Although I have criticized the way you presented your conclusions, I did not insult you.

    Your putting me on time-out for 24 hours is unethical and an abuse of your power as a moderator. Shame on you. That’s the kind of behavior we’d see in a dictatorship.

  • Cry me a river. I felt bad for you because no one else had taken your bait, so I indulged you briefly. And this is the thanks I get. Sheesh.

  • Gary Whittenberger

    I am not thanking you. I am chastising you for your abuse of power as a moderator.

    Also, you hide behind a fake name. Present your real name so that we can know for sure who is behaving badly.

  • Where did you get the wholly mistaken idea that I’m obliged to jump through hoops for you or be tolerant of your childish conduct? If you want to make the rules and bark orders at people, get your own blog.

  • Gary Whittenberger

    My conduct is not childish at all. It is civil and rational.

    You are obliged to jump through some hoops according to the norms of civil rational discourse. When you are asked for supporting evidence for a claim you make, then it is your responsibility to present it, not dodge the request and censor the person asking for it.

    If you want to make the rules, then make sure that they correspond to sound norms for civil rational discourse. Hiding behind a fake name lowers your credibility and increases the probability that you will be uncivil, authoritarian, or both. Come out of the closet, Shem the Penman.

  • I don’t know how much more emphatically I can suggest that you start acting in a more civil way here. This isn’t your blog, Gary. If you want to tell yourself you’ve been “censored” for your commitment to the truth rather than reprimanded for your harassing and overbearing behavior, you can do it elsewhere.

  • Gary Whittenberger

    I don’t know how much more emphatically I can suggest that I am acting in a very civil way. This is your blog, and it’s about time that you start to manage it properly. You censored me for 24 hours. I don’t need to tell myself that. You confessed.

    I suspect you are preparing to either put me into time out again or ban me from your blog. That would be consistent with your prior behavior. And you hide behind the mask of anonymity.

  • Take the weekend off. And lighten up.

  • al kimeea

    Racism isn’t forensic science, but can drive an investigator to interpret the available evidence, even manipulate it, to gain an arrest. Same for the prosecutor who’s also driven by his job depending on convictions, especially in election season.

    Forensics as portrayed in entertainment is laughable. Reading the blogs and comments of those doing this work outside the idiot box, you learn there is much, much dramatic license on display. Two different shows had a lab ass inject silicone, used to cast footprints, into stab wounds in the chest. Once it set, VOILA!!! A nearly exact cast of the blade. From soft tissue. Laugh out loud.

    At the same time, DNA has freed many people imprisoned because the original detective had a strong gut feeling.

    SP – Like any other science, forensics is about inference, not evidence.

    What should we infer from Hiroshima & Nagasaki in regards to E=mc**2? Are they not evidence of the validity of Albert’s ideas? How about gravitational lensing? Not evidence, even though it has been observed many times?

    You write about science as if it’s a thing unto itself, merrily going about its business as if there are no people with their hands up its arse, having it say what they’d like it to say for money, fame, power,…, oppression…

  • al kimeea

    the name is unimportant as is any other detail about anyone – only what’s being said about this or that in the marketplace of ideas

  • Gary Whittenberger

    No, the name is important in any communication situation. The reputation of the person, correctly named, should rise or fall dependent on the quality of his ideas and the civility of his behavior.

    Other details which may be important are credentials.

  • al kimeea

    I don’t look at it that way, unless you want to get down to the nitty-gritty.

    We’re just shootin the breeze over a few beers. Your are entirely unknown by me, so your name has had no influence on my ponderings on what you’ve said.

    Shem the Penman seems to be a masculine handle. But it doesn’t matter to me and I really don’t think it should. Also, Shem is not the first to make arguments like this either. I know he’s working off of ideas of those who came before.

  • Gary Whittenberger

    AK1: I don’t look at it that way, unless you want to get down to the nitty-gritty.

    GW1: Sure, let’s get down to the nitty-gritty.

    AK1: We’re just shootin the breeze over a few beers. Your are entirely unknown by me, so your name has had no influence on my ponderings on what you’ve said.

    GW1: First, this forum is much more advanced than “shootin the breeze over a few beers.” Secondly, still even in that situation, strangers should exchange names at the beginning.

    AK1: Shem the Penman seems to be a masculine handle. But it doesn’t matter to me and I really don’t think it should.

    GW1: It also doesn’t matter to me whether Shem is a man, a woman, or something in-between. What matters is his real name and sometimes credentials. When people give their real names, they are more likely to be civil. Why? Because if they are uncivil, it attaches badly to their reputation.

    AK1: Also, Shem is not the first to make arguments like this either. I know he’s working off of ideas of those who came before.

    GW1: That’s irrelevant. Is “al kimeea” your real name? If so, why? If not, why not?

  • al kimeea

    First, this forum is much more advanced than “shootin the breeze over a few beers.”

    I’ll ask the barkeep. Shem?

    Also, I’m pretty sure I’m in slight agreement with Shem because people make mistakes and one should always question the authorities, being a member of law enforcement is no magic pill against bias.

    A lawyer told me there’s no evidence for Einstein. None. It’s all conjecture…

    Forgot

    No, not my real name. It is Arabic for alchemist. You know why not, I just told you. People have lost their jobs for expressing godless ideas as well.

  • srh1965

    “GW1: Low income defendants will be appointed an attorney if they cannot afford one. This attorney always has the opportunity to challenge evidence and forensic science itself.” Are you being serious? The quality of state-appointed attorneys is notoriously low; plus that attorney is the only support that many defendants have against the massive resources of the state.

    “GW1: Nonsense! Forensics is about evidence and inference. It is also about the basic science and training.”
    If only that were so simple. Forensics is mostly not science at all.

    “Science has no interest in protecting the powerful; that is irrelevant to science. ”
    Again, if only that nice view were true. But the people who pursue science are motivated in many different ways. The great imbalance of resources in forensics is tilted massively towards the prosecution, self-evidently.

    Really Gary, if these arguments are your best, you must take some time to read the literature. Forensics is in disarray the world over, as its former authority has been shown to be based on little more than guesswork in many cases. It has resulted in large numbers of miscarriages of justice and, in your benighted land, the death of innocent people at the hand of your government.

    http://lst.law.asu.edu/FS09/pdfs/H.T.%20Edwards,%20Solving%20the%20Problems%20That%20Plague%20Forensic%20Science.pdf
    https://www.innocenceproject.org/causes/misapplication-forensic-science/

  • srh1965

    Excellent post. GW appears to place an almost religious faith in both the quality of forensics as a discipline and in the good faith of the people involved.

  • Thanks. It’s not surprising, given the amount of authority that forensics has attained through TV shows and movies, that people find it difficult to accept that the methods aren’t quite as airtight as they’ve been led to believe.

    But there’s a deeper issue here that creates an even bigger obstacle, and that’s the fact that forensics is pretty much indistinguishable from science. Questioning the precision and accuracy of forensics, therefore, is tantamount to questioning the objectivity of scientific inquiry itself.