
Abnormal Brain Structure In Youth Who Commit Homicide - signa11
http://www.ncbi.nlm.nih.gov/pubmed/24936430
======
brandonb
I love this type of research, but this particular study requires a two-ton
grain of salt.

First, these results are based on only 20 total homicide offenders. So when
they claim they can classify 75% of murderers correctly, that really just
means 15 out of 20.

Second, the final classifier has access to more than 14 variables, including
factors like the number of previous convictions, not just brain structure. [1]

If you're fitting 14 variables to 20 data points, it's very likely you're
over-fitting. I personally would wait for a much larger study before drawing
conclusions.

[1] "The identified variables were age, PCL:YV Factor 1, PCL:YV Factor 2,
years of regular substance use, total number of convictions, ICU, SES, brain
volume, left and right lateral orbital frontal cortex, medial orbital frontal
cortex, anterior and posterior cingulate, right temporal pole, and right and
left parahippocampal cortex."
[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4055901/](http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4055901/)

~~~
anigbrowl
20 total homicide offenders, 135 non-homicide offenders, and two control
groups comprising another 41 subjects between them. I agree it's a highly
preliminary result, but successfully IDing 75% of homicide perpetrators and
82% of non-homicide subjects is a good start. Why are you leaving out the rest
of the test population?

PS I don't think it's perfect by any means, when you look at the population
it's pretty particular to New Mexico. Per my other comment, I think the
significance of this is that we should be doing a lot more research in our
depressingly large incarcerated population to develop a better understanding
what makes some criminals dangerous vs others who are just selfish or
opportunistic.

~~~
mewse
75% of homicide perpetrators identified correctly (15/20) + 82% of non-
homicide perpetrators identified correctly (111/135) is a total classification
accuracy of 81% (126/155) for the procedure.

But if we just assume that everyone is in the non-homicide group (which is
what "innocent until proven guilty" has us do anyway), then that gives us a
total classification accuracy of (135/155) 85% for the same sample set. That
is, "innocent until proven guilty" is notably _more_ accurate than the system
which is being proposed here, and infinitely less likely to deliver a false
positive result.

~~~
anigbrowl
It can't be infinitely less likely to produce a false result or we'd never
have miscarriages of justice. Current research estimates the rate of false
positives in capital crimes (almost all of which are homicides) at 4.1%.
[http://www.pnas.org/content/early/2014/04/23/1306417111.full...](http://www.pnas.org/content/early/2014/04/23/1306417111.full.pdf)

But the point here is that _chance_ is only 50%, so if we have a mechanical
system that's within shouting distance of matching our extremely elaborate and
very expensive trial system then that's noteworthy. 81% is not far away from
87%; what happens when the machine learning system can repeatably identify
homicidal behavior with greater accuracy than our criminal justice system?
Overall accuracy is highly significant because it will create a lot of
pressure to identify murderers in the interests of public safety. Of course we
shouldn't rely on such a system because of the risk of false positives, but
you'll see attempts to bring it into evidence in more and more cases. If/when
such a system starts to outperform the existing on in terms of having a lower
number of false positives, then every innocent defendant is going to demand it
and every guilty defendant (in the legal sense) will cite it as a mitigating
circumstance.

------
DasCorCor
I could have acheived better accuracy (87%) by simply calling everyone a non-
murderer.

~~~
the_cat_kittles
two people have the opportunity to invest in 20 startups. the first person
says no to all of them, and the second person invests in all 20 of them. all
but one go bankrupt. the first person proudly proclaims "i can avoid bad
investments with 95% probability!"... and the second is a millionaire.

~~~
reinhardt
Nobody became millionaire by calling everyone a murderer.

~~~
the_cat_kittles
just pointing out that the "success" of your model depends heavily on how you
choose your evaluation criteria. to me, 87% correctly classified seems
irrelevant because you can just change the distribution of murderers and non
murders and your model would fail. it seems more interesting to me to focus
on, say, the rate the model successfully classifies murders.

~~~
slavik81
The risk structure is different. When you make an investment in a company that
turns out not to be successful, you wasted your money. If you persecute
someone who would never have murdered anyone, you may have done great and
irreversible harm an innocent man.

The rate at which it correctly classifies non-murderers is more important for
this measure to be useful.

------
hackuser
From the report:

"Here we use neuroimaging and voxel-based morphometry to examine brain gray
matter in incarcerated male adolescents who committed homicide (n = 20)
compared with incarcerated offenders who did not commit homicide (n = 135).
Two additional control groups were used to understand further the nature of
gray matter differences: incarcerated offenders who did not commit homicide
matched on important demographic and psychometric variables (n = 20) and
healthy participants from the community (n = 21)."

Perhaps someone with expertise can comment on a couple of points:

1) Am I correct that this research is preliminary, given the number of
subjects involved? It seems too preliminary to even report on HN (to answer my
own question), but maybe I don't understand it well enough.

2) Is there reason to believe that the brain differences caused the homicide,
rather than believe that committing homicide and getting incarcerated, two
very traumatic events, caused changes to their brains? Or that something very
traumatic caused them both the crime and the brain changes?

~~~
yoz-y
Given a sufficiently high number of input parameters (huge in this study) and
a sufficiently small test group (tiny, in comparison to number of parameters
in this study), any classifier black-box approach will find some correlation
in any arbitrary condition.

[http://blogs.discovermagazine.com/neuroskeptic/2009/09/16/fm...](http://blogs.discovermagazine.com/neuroskeptic/2009/09/16/fmri-
gets-slap-in-the-face-with-a-dead-fish/#.U7zcthYucuJ)

------
BadassFractal
In his book "Free Will" ([http://www.samharris.org/free-
will](http://www.samharris.org/free-will)), Sam Harris discusses the dilemma
of what we would do if we suddenly discovered that horrible acts of violence
were actually pre-determined by one's genetics and physical traits, rather
than by one's (supposedly) controllable will and thought processes.

How do you punish someone who unwillingly commits atrocities, someone who
cannot control it and didn't ask to be born that way? What do you do with that
individual? IIRC the example was someone committing a murder and then the jury
discovering that the person actually had a brain tumor that was making him/her
act differently from normal. Do you hate that person? Who do you blame?

In an ideal futuristic society we would be able to alter our genetics in such
a way that we do not present an unnecessary threat to others, if we do indeed
discover that we're naturally predisposed towards horrible acts of violence.

~~~
hrjet
>How do you punish someone who unwillingly commits atrocities

I look at justice more as a "confinement of the criminal behavior" than
"punishment of the criminal". Viewed that way, I don't see a dilemma in being
able to better identify the behavior, especially if the confinement is done
after a criminal act.

~~~
serf
in my opinion more should should share your idea of justice. It's sad that the
thought processes behind high-profile criminal justice are typically fueled by
the desire to punish, by whatever society at large.

------
downandout
While 75% of homicide defendants may have this defect, the opposite is almost
certainly not true (that 75% of people with this defect will commit homicide).
This type of research is fascinating, but since we have no way to treat such a
condition, its only purpose would be to attempt to identify potential
murderers. And that is a very slippery slope (see Minority Report).

------
anigbrowl
This doesn't surprise me, sadly...

 _incarcerated homicide offenders had reduced gray matter volumes in the
medial and lateral temporal lobes, including the hippocampus and posterior
insula_

...and indeed I've wondered why we don't test for conditions in the
incarcerated population that have known potential for altering behavior, eg
_Toxoplasma gondii_ see
[http://wwwnc.cdc.gov/eid/article/9/11/03-0143_article](http://wwwnc.cdc.gov/eid/article/9/11/03-0143_article)
for example.

Assuming for the sake of argument that we could soon reliably identify
symptoms of a homocidal disposition, what does this mean for criminal justice
and law enforcement? From a purely utilitarian point of view it makes sense to
monitor or even confine such people, but from a libertarian (philosophical)
point of view, we could not subject them to penal confinement as people can
hardly be held criminally liable for deficiencies in their own brain
structure, which might be the result of genetics, malnutrition, or childhood
trauma.

Some sort of medical incarceration is the obvious alternative, but this is
legally problematic. A Supreme Court case _O 'Connor v. Donaldson_ (1975)
(among others, but this is the big one) made it very difficult to commit
someone for confinement in a mental institution without clear evidence that
they present a danger to society. Arguably, the US went putting people in
mental institutions too casually and without regards for their rights, to a
position of not providing sufficient mental health services for all but the
most unhinged patients. While this technological advance might one day provide
a reliable gauge of a person's homicidal capability, that's a long way from
identifying how or when such behavior might manifest.

At a less extreme case than confining someone, should we allow someone with a
measurable homicidal tendency to purchase guns? If we forbid them doing so,
how do we avoid a tiered approach to citizenship, in which the rights of some
are abrogated pre-emptively through no fault of their own actions, but a
'fault in their stars'?

From a different angle, this is also an interesting result for attorneys
involved in death penalty defensive work - if MRI scans, which the courts and
public are highly familiar with, can reliably predict homicidal
characteristics, then the question of criminal responsibility becomes much
more difficult to answer, since people have no control over the structures of
their own brains.

~~~
XorNot
Well, and this is just a crazy idea here, you could just decide as a society
that citizen gun ownership is kind of pointlessly dangerous, with a close to
statistically insignificant rate of self-defense usage, and instead move back
to a model of an actual well-regulated militia.

~~~
anigbrowl
We could, but I'm trying to take an 'all other factors being equal' approach
so as to minimize the number of assumptions required, and so considered the
second amendment issues in terms of how they're currently interpreted rather
than how that interpretation might change.

------
VladimirGolovin
One of the authors of the paper is Dr. Kent Kiehl, who is famous for using a
mobile fMRI to scan thousands of inmates in multiple prisons, including many
psychopathic offenders.

His book on his research of psychopathy in prisons, "The Psychopath
Whisperer", is excellent (despite a terrible name). Easily one of the best
books on the topic. I want a sequel.

------
putlake
In recent years research has found more and more evidence of genetic
determinism. i.e. certain types of brains are more prone to violent behavior.
Psychopaths also have a certain brain "signature" [1]

I wonder if the legal system recognizes genetic determinism as a mitigating
factor in violent crimes. If I were a defense attorney in a no-win scenario,
I'd probably try this defense. Ah..will probably spend the rest of the night
researching [2]

1\. [http://www.smithsonianmag.com/science-nature/the-
neuroscient...](http://www.smithsonianmag.com/science-nature/the-
neuroscientist-who-discovered-he-was-a-psychopath-180947814/)

2\. [https://www.google.com/webhp?sourceid=chrome-
instant&ion=1&e...](https://www.google.com/webhp?sourceid=chrome-
instant&ion=1&espv=2&ie=UTF-8#q=brain+neurology+as+a+defense+in+violent+crimes)

~~~
gatehouse
predisposition to murder doesn't seem like a good reason to let someone go
free

~~~
sliverstorm
_It 's not his fault, he can't resist murdering! How could we imprison a man
like that!_

------
carlob
How do they know the different brain structure is not an effect of having
committed an homicide rather than the converse?

Can someone with access to the full text see if they address this question?

~~~
jeromeparadis
I was wondering the same thing. Also, isn't it possible that how they lived
and in which environment before committing a murder affected their brain?

------
math0ne
Watch out the future police are coming for you!

------
bakhy
I hate the way the word "abnormal" is thrown around just like that. I would
bet that any group of people with a strong common characteristic could be
found to have common "abnormalities" in their brain.

<Morgan Freeman>Does this average, normal brain, actually exist? Do the heads
of more than 50% of people on Earth contain close to identical brains? Or are
we all abnormal in our own way?</Morgan Freeman>

And their tendentious conclusion about predicting homicide is simply creepy.

