Criminal Psychology: What are the Limits of Psychological Profiling?

   Sorry I've been gone for a while but I'm back with an excursion into the world of criminal psychology, much beloved by crime writes (Poirot for example, was basically a very good criminal psychologist). The idea of psychological profiling has always intrigued me, being able to massively reduce the suspects for a crime by deducing the personality and habits of the perpetrator would be an invaluable tool in forensics.

   The first thing to remember however is that a psychological profile can never be used as proof, only as a technique to gain hard evidence. This is because psychological profiling, even by the standards of forensic science, is a very young field with very few standardised methodologies, and even less scientific reliability. this makes the use of a profile as evidence usually a violation of rule 702 of the Federal Rules of Evidence.  Rule 702 states that expert testimony can only be allowed in court when:
 1) the testimony is based on sufficient facts or data
 2) the testimony is the product of reliable principles and methods
 3) the witness has applied the principles and methods reliably to the facts of the case.
   As such there are very few cases where you'd be able to convict on the basis of a criminal profile no matter how well you suspect fits it.

   Even with this caveat, criminal profiling is far from perfect. In fact for a scientific field it's positively riddled with problems. The main problem comes from the fact that the only standardised method of psychological profiling was created by Ressler and Douglas, who were commissioned by the FBI. They interviewed 36 serial killers who had been caught and imprisoned to draw up a list of statistics for the 'average' serial killer. There are several problems with this technique:
   1) The data pool is absurdly small, which leads to large confidence intervals and an inaccurate data pool to draw conclusions from.
   2) The tested group leaves out n important demographic, serial killers who haven't been caught. The 'type' of serial killer who manages to avoid capture (the one where profiling would probably be more needed) is totally absent from the data.
   These inaccuracies can lead to serious mistakes on behalf of the criminal profiler, which could be potentially lead to false convictions or releases if they were taken as hard evidence. For example, there was a case in 2002,of the Washington D.C. snipers, where the killer was predicted to be a white male working alone and turned out to be a father-son duo of black men. "Woops" would be an understatement.

   However there are upsides and success stories. First thing's first, Ressler and Douglas's experiment is ongoing, as the FBI interview more and more serial killers, expanding the pool and aiding with half the problems mentioned above. Psychological profiling can also be used to discover serial killers by linking cases, and showing there is a common killer, and there must be a reason that the FBI continues to fund it.

   Overall Criminal Psychology, while being a useful tool, should never be viewed as hard evidence and regardless of validity will almost always bias the jury. Despite all the criticism listed I believe science gives us the final word in the form of a study by Kocsis which showed that, in detecting criminals, criminal psychologists did have an almost 20% higher validity rate than the closest group, students (72 to 59%). Always consider psychological 'evidence' and always take it with a grain of salt. As always thanks for reading, over and out.

Strychnine

Strychnine is practically synonymous with poison in peoples' minds, due in no small part to crim and murder mystery author. Despite this it is an unlikely choice for a poison as it has an extremely bitter taste.

Name: Strychnine

Chemical Formula: C21H22N2O2

Effect On Victim: Acute Strychnine poisoning effects usually appear very rapidly (10-15 minutes). It starts with muscle stiffness of the back or neck. This is followed by tremors and twitching, and then convulsions. These convulsions are extremely painful, lasting about a minute, and can be accompanied by momentary asphyxiation due to convulsions of respiratory muscles. There's normally a 15 minute rest interval between each convulsion, however the victim will be both exhausted and terrified as a side effect of strychnine include heightened awareness (and the convulsions are violent enough to cause your head to touch your heels, so that's already pretty scary). Death is caused by spasming of respiratory lungs causing asphyxiation.

Strychnine is a scary neurotoxin which mainly affects the nerves in the spinal chord. It binds to neuroreceptors in the spinal chords (it's an antagonist). this causes the neurones to trigger too much as it requires much less glycine, which is the usual trigger, to cause them to activate. This results in the massive convulsions. The victim may also vomit (such a common symptom of poisoning) as that is the body's only way to rapidly excrete the poison.

Lethal Dose:  As little as 30mg can be fatal.

Diagnosis: There are usually no signs of Strychnine in the body post mortem, except that the jaw is occasionally twisted in a death grin. However Strychnine does stay in the body for a long time and can be detected through the use of a dry chemistry process using tandem ion tap mass spectometry. You will find peaks at 334, 319, 306, 277, 261, 246, 233 and 220.

The velos pro dual ion-trap spectroscope is the weapon of choice for identifying strychnine

That's the theory and method behind identifying one of the scariest poison out there. I can see why writers like Agatha christie are so fond of it, it's pretty dramatic. Over and out, as always feel free to comment, until next time!