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Archive for the ‘Forensic evidence’ Category

Dexter murdererNo, this isn’t one of those conversation starters for dinner table conversation although you can feel free to use it as such. Actually, it would likely go better with after dinner drinks. It’s a bit too daunting for dinner.

It’s long been advised (at least in forensic psychology circles) that when it comes to staying alive, you really want to steer clear of any psychopath with a low IQ who is abusing drugs and/or alcohol. It just isn’t going to end well. That was more common wisdom though (provided to those who wondered what the best policy was when dealing with unintelligent, drunk psychopaths) and now (ta-da!) we have actual research to prove it.

Researchers at Northwestern, DePaul and the University of Illinois at Chicago examined 77 inmates (90% male, 68% African-American, average age of 32 with a range of 16 to 67 years, and an average of 10.5 years of education) who were incarcerated in Illinois and Missouri. They sorted these inmates (who had either been charged with or convicted of the murders of 137 different people) into two groups: the affective/impulsive group and the premeditated/predatory group using Meloy’s forensic criteria (included in the article’s Appendix) related to psychopathy. The authors further define the group assignment as follows:

Predatory/Instrumental violence is “a planned, purposeful, and primarily cognitively derived act, whereas Affective/Impulsive violence refers to reactive, immediate, and primarily emotionally derived acts”.

Every inmate tested had been referred by their attorney or by the court for neuropsychological evaluation related to fitness to stand trial, criminal responsibility, mental retardation or neuropsychological abnormalities. The referrals were made across all phases of trial and all evaluations were completed between 2000 and 2007. Only one inmate was eventually found to be NGRI (not guilty by reason of insanity) by the court. The researchers were interested in examining the neuropsychological and intelligence differences, if any, between these two groups of both accused and convicted Defendants. All inmates participated in a clinical interview and completed a neuropsychological test battery. (For those interested in such things, the test battery included the Wechsler IQ test [WAIS-III]; subtests of the Wechsler Memory Scale, Third Edition; California Verbal Learning Test, Second Edition; Wisconsin Card Sorting Test, Conners’ Continuous Performance Task II, the Trail Making Test, the Stroop Color and Word Test, and the Controlled Oral Word Association Test. In short, they took a lot of tests.)

Here is what the researchers found upon comparing the two groups:

Affective/Impulsive Defendants were younger, less educated, more likely to be African-American, more likely to have a history of substance abuse (93% to 76%) or developmental disorders and less likely to have a history of psychiatric diagnosis or personality disorder than were those Defendants in the Predatory/Instrumental group.

Affective/Impulsive Defendants had lower overall IQ scores (79, in the Borderline Range) while Predatory/Instrumental Defendants scored in the Average Range (93).

Affective/Impulsive Defendants had lower overall memory retention, lower scores on attention and task completion, and poorer face recognition.

Affective/Impulsive Defendants had lower problem-solving efficiency and cognitive flexibility.

Predatory/Instrumental Defendants were more likely to have both Axis I (major mental disorders such as Schizophrenia or Bipolar Disorder) and Axis II disorders (personality disorders such as Antisocial, Narcissistic, Histrionic, Borderline, and so on).

The researchers say what all this means is that Affective/Impulsive Defendants have “significant neuropsychological and intellectual deficits” while Predatory/Instrumental Defendants are “largely intact across neurocognitive domains”. In English, that means the Affective/Impulsive Defendants had multiple mental and developmental problems while the Predatory/Instrumental Defendants were “pretty much okay” when their intellectual and neurocognitive functions were assessed–but, of course, very much not okay on measures of what constitutes empathy for others.

So, planful murderers are most likely the predatory type, and the emotional/low intellect murderers tend to be the impulsive types. The former is likely to be smarter, and a bit less likely to be caught (or at least less quickly caught). The emotional/impulsive murderer is likely to commit the crime with less thought to the consequences, and without a plan for succeeding at it.

Our sage counsel is for you to stay away from both groups and away from psychopaths in general.

Hanlon, RE, Brook, M., Stratton, J., Jensen, M., & Rubin, LH (2013). Neuropsychological and intellectual differences between types of Defendants: Affective/Impulsive versus Predatory/Instrumental (Premeditated) Homicide. Criminal Justice and Behavior, 40



Shoot first and draw the target second

Monday, February 4, 2013
posted by Douglas Keene

sharpshooter fallacyFact is often stranger than fiction and living here in Texas–we often hear tall tales. Some of them are true while most are pulled out to illustrate a point. Some are colorful and amusing while others take on a life of their own as representative of logical fallacies. Like the Texas sharpshooter tale where you shoot first and later draw the bullseye around the holes left by your bullets. You appear to be a sharpshooter but anyone drawing that conclusion would be sadly mistaken.

The Texas Sharpshooter Fallacy is a variation of what we joked about when I was in graduate school where we referred to this as “drawing the curve before you plot the data”. This logical fallacy is really about making assumptions when you only have partial data or circumstantial evidence. And if you’ve ever watched mock jurors or real jurors–you know this is a common occurrence as trial narratives are presented. If there’s a hole in the story–someone is bound to jump through it.

It’s a funny thing. After almost two decades of doing trial consulting, we know for sure that you can’t always predict how a group of twelve is going to respond to a story. And even when you predict with general accuracy, you don’t always know ‘why’ they would ultimately come to the conclusion they reach.  For example, it can be startling how quickly leaps can be made to conspiracy and how persuasive conspiracy theories can be given the right group of jurors.

Whether it’s the Texas sharpshooter fallacy or some other logical fallacy your case narrative elicits–you want to figure out how to plug those gaps in your story and how to identify what sort of person is going to identify a conspiracy where there is none and confuse your other decision makers during deliberation. That conspiracy-prone [“I see a pattern here!”] potential juror is a terrific target for your peremptory strikes. You could even think of pretrial research as shooting bullet holes and then drawing your targets on the jurors who shot them.



Do not pursue a life of crime. And that advice goes beyond the idea you would be too easy to smell. And way beyond the tired recommendation of heavy-duty, clinical strength antiperspirant (although far be it from us to dissuade you from smelling nice). This is instead, as is our tendency here, a recommendation based on research.

Researchers from the Hebrew University of Jerusalem found a way to lift high-quality fingerprints from soaking wet paper. As it turns out, the amino acids in some human sweat can degrade fingerprint quality. In the past, therefore, the sweaty criminal may have been tough to identify. But progress is being made!

In this study, the scientists fixed this problem by making the gold nanoparticles stick to the paper upon which the fingerprint is located, instead of to the print itself. This method, detailed in the November issue of the German journal Angewandte Chemie [Applied Chemistry], results in a negative image of the fingerprint, with the particles sticking to the divots between the fatty ridges formed by greasy fingers. Since fat is impermeable, the ridges stay in place even when faced with massive amounts of water. You can read a detailed description of why this is so tough to do over at the Salamander Hours blog.

It would seem that sweaty criminals have a short time frame for choosing new career paths. So why is this important for litigation advocates to know?

Because it represents a significant advance in finger-printing technology and fingerprint identification.

It is a sign of moving closer to catching criminals whose amino acids may have unwittingly helped them to escape detection up until now.

Plus–there are times when it’s good to know something a little amusing and yet ostensibly relevant for litigation advocacy.

Jaber N, Lesniewski A, Gabizon H, Shenawi S, Mandler D, & Almog J (2012). Visualization of latent fingermarks by nanotechnology: reversed development on paper-a remedy to the variation in sweat composition. Angewandte Chemie (International ed. in English), 51 (49), 12224-7 PMID: 23125068

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The work of the Innocence Project gets a lot of attention. Justifiably so. But did you know that DNA evidence plays no role whatsoever in 90-95% of convictions and therefore, cannot be used to pursue future innocence claims? Pacific Standard has an informative review of non-DNA exonerations that is worth a read.

They talk about EXI–the Exoneration Initiative, a project that takes on cases without DNA evidence in an effort “to exonerate the actually innocent”. Prosecutors work hard to maintain and protect the conviction. As difficult as exonerations are when DNA evidence is available, it is far more difficult without it. Exoneration efforts consume thousands of volunteer work hours and can take years to resolve.

Their cases sometimes hinge on false confessions experts who do are expensive, and who are often not allowed to testify in court. Other times their cases revolve around challenging eyewitness or informant testimony, forensic evidence, the conduct and actions of the arresting or investigating police officers and prosecutors or defense attorneys. As prosecutors and criminal defense attorneys know, once a jury renders a guilty verdict, the accused is now the convict, and all assumptions of innocence cease. The bar is set very high for reversal and exoneration, and achieving this result is exceptionally difficult.

We’ve written about false confessions before and have recommended a non-fiction account by Ray Bonner on wrongful conviction as well as a fictional account from John Grisham. There is nothing entertaining however, in the realities of being imprisoned for a crime you did not commit.

As we’ve listened to mock jurors struggling to comprehend false confessions and why anyone could possibly confess to a heinous crime they did not commit–the hopelessness that is the life of the wrongfully convicted becomes palpable. Even when jurors are told there is no dispute about the person’s innocence–it is hard for them to accept. “Then why was there a confession?” They are appalled at such an extreme miscarriage of justice. But many of them are just as appalled that anyone would falsely confess and thus, they see the false confessor as having significant responsibility for their subsequent conviction and incarceration. Among some, it is easier to blame the victim of false imprisonment than to imagine that the system could go so horribly wrong.

Recently, we listened to mock jurors struggle with a case like this and were surprised to hear reality TV actually educating the mock jurors about the pressures of the interrogation room. Two of the mock jurors watched a show called The First 48 on A&E Television. Evidently, they watched it a lot, and boy did they like it! They were able to describe the “real-life” pressures in the interrogation room and make the idea of a false confession make more sense to the other mock jurors. As one skeptic said, “Well, obviously I know it can happen because I’ve read about DNA exonerations–but it still makes no sense to me that anyone would confess to murder when they didn’t do it. What was wrong with him?” There was no sympathy for the cascade of errors often seen in wrongful conviction cases (e.g., evidence errors, witness errors, police errors, and more) but there was also little sympathy for the man who’d lost his entire young adulthood, both parents and a sibling to his (wrongful) time in prison. “If he had just stood his ground and not confessed, we wouldn’t be here now!”

It’s a nightmare you cannot escape. Kafka comes to mind… Day after day after day. Having advocates like the Innocence Project or the Exoneration Initiative after such a miscarriage of justice is truly a ray of sunlight in a very dark (and typically very, very long) time. Pursuing the evidence needed to free the wrongfully convicted is often a thankless job until an exoneration is granted. That happens more often for the Innocence Project than it does for the Exoneration Initiative–just because of the nature of their focus. We want to thank both of them. They keep showing up after everyone else has gone home.


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DNA seals the deal. Period. Maybe.

Wednesday, October 24, 2012
posted by Douglas Keene

Or does it? Perhaps not. DNA evidence is powerfully convincing perhaps becausewe’ve come to accept the idea that DNA is a sort of individual genetic ‘serial number’ that just needs to be ‘read off’ from a biological sample — but the reality is far more complex”.

Vaughan Bell (who usually writes on the Mind Hacks blog) has an article in the Examiner that alerted us to a study showing how even DNA forensic matching results are often decided in a “judgment call” and not by simply reading off the ‘genetic serial number’. DNA samples obtained at crime scenes may be the DNA of two or more people mixed together. It isn’t simply the victim’s DNA, the perpetrator’s DNA and the roommate’s DNA. It may be all three mixed together. These are called, fairly predictably, “mixed samples”. Vaughan describes the study by Itiel Dror and Greg Hampikian:

In Dror’s study, DNA experts were given results from a mixed sample that was drawn, unknown to them, from a previous real-world case that hinged on whether suspects were present at the scene. After analysing the samples, they not only disagreed with one another but also came to different conclusions depending on whether they had information about the case, or whether they had nothing to go on but the genetic data.

It is worth noting that these findings do not invalidate forensic evidence. Studies also show that despite biases, identification is mostly done reliably, but the fact that outside information can affect decisions remains a worry for the justice system. 

Perhaps, not surprisingly, Vaughan’s explanation is much easier to understand than the actual article itself. It’s a good reminder that just like forensic evaluations of legal sanity (or insanity) are somewhat idiosyncratic and reflect the individual examiner’s judgment calls–so, apparently, are the analyses of mixed DNA samples. The story (aka case narrative) needs to make sense without the DNA evidence. Often, what seems to happen, is that the story is tweaked to match the DNA evidence since “DNA doesn’t lie”.

That’s right. DNA doesn’t lie. But it’s clear we don’t yet know exactly how to talk DNAs complex language so we might misinterpret.

If you want to reinforce the credibility of the DNA evidence, refer to it as fact, and frame your trial story with that ‘fact’ as a premise for the other aspects of the story. Jurors are likely to use hindsight bias, based on knowledge of the DNA evidence, to reinforce their views of the non-DNA facets of the story.

Dror IE, & Hampikian G (2011). Subjectivity and bias in forensic DNA mixture interpretation. Science & Justice : Journal of the Forensic Science Society, 51 (4), 204-8 PMID: 22137054