typodupeerror

## Statisticians Uncover the Mathematics of a Serial Killer164

Hugh Pickens writes writes "Andrei Chikatilo, 'The Butcher of Rostov,' was one of the most prolific serial killers in modern history committing at least 52 murders between 1978 and 1990 before he was caught, tried, and executed. The pattern of his murders, though, was irregular with long periods of no activity, interrupted by several murders within a short period of time. Hoping to gain insight into serial killings to prevent similar murders, Mikhail Simkin and Vwani Roychowdhury at UCLA built a mathematical model of the time pattern of the activity of Chikatilo and found the distribution of the intervals between murders follows a power law with the exponent of 1.4. The basis of their analysis is the hypothesis that 'similar to epileptic seizures, the psychotic affects, causing a serial killer to commit murder, arise from simultaneous firing of large number of neurons in the brain.' In modeling the behavior the authors didn't find that 'the killer commits murder right at the moment when neural excitation reaches a certain threshold. He needs time to plan and prepare his crime' so they built delay into their model. The killings eventually have a sedative effect, pushing the neuronal activity below the 'killing threshold' – which is why there are large intervals of time between groups of murders. 'There is at least qualitative agreement between theory and observation [PDF],' conclude the authors. 'Stats can't tell you who the perp is, but they're getting better and better at figuring out where and when the next crime might happen,' writes criminal lawyer Nathaniel Burney adding that 'catching a serial killer by focusing resources based on when and where he's likely to strike next is a hell of a lot better than relying on the junk science of behavioral profiling.'"
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## Statisticians Uncover the Mathematics of a Serial Killer

• #### Great. So now all we need... (Score:5, Insightful)

on Tuesday January 17, 2012 @04:15AM (#38722252)

...is another series of murders to consolidate the theory.

Any takers?

• #### Re:Yeah I saw that on... (Score:5, Insightful)

<plasticfish DOT info AT gmail DOT com> on Tuesday January 17, 2012 @04:17AM (#38722258) Homepage

Dear teeloo,

Many of us reside outside the US and/or have lives.

Sincerely,

The rest of /.

• #### They have 1 data point (Score:5, Insightful)

by Anonymous Coward on Tuesday January 17, 2012 @04:26AM (#38722300)

Aren't they jumping the gun a bit?

• #### always some correlation to a single set of data (Score:5, Insightful)

on Tuesday January 17, 2012 @04:45AM (#38722360)
If you look hard enough you can always find some function that correlates to a single set of data. Like the analogy in a beautiful mind [imdb.com], you can find any pattern or picture in the stars if you look hard enough.
• #### Re:Sounds like the dude... (Score:5, Insightful)

on Tuesday January 17, 2012 @05:04AM (#38722420)
Being married/having girlfriends does not imply getting laid. They can quite often be mutually exclusive sets. Some men are driven to drink, use drugs, post on slashdot in such situations. Others may be driven to commit homicide.
• #### Power law not usefully predictive in this case (Score:5, Insightful)

on Tuesday January 17, 2012 @05:05AM (#38722424)

I think the importance of what they found is overstated. The fact that a murderer's patterns fit a power law is not particularly helpful in really pinning down the time of the next murder. "The expected time of the next murder is a distribution of odds along this curve" is not particularly useful in trying to stop a single crime. Power laws are more useful predictors when applied across populations.

While unlikely to ever be predictive, this result is more interesting from a more academic perspective. It could help illuminate what might be going on in the brain of a serial murderer. Learning how damaged brains function (or fail to function) has long been a means of studying how non-damaged brains may work.

So this might provide some insight into how a compulsive thought builds up in the brain, but it's unlikely to ever allow a profiler to say "stake out this intersection on this night".

• #### Re:always some correlation to a single set of data (Score:5, Insightful)

on Tuesday January 17, 2012 @05:05AM (#38722428) Homepage Journal

True. The power law, though, is a particularly dangerous and entrancing trap to fall in to. Almost everything in nature - from pure randomness to highly structured effects - can be fitted to a power law. You often don't even need to do any transformation of the data - simply choosing the wrong set of dependent and independent variables to examine can do it.

My favourite goto whenever this subject comes up is the essay "So You Think You Have a Power Law - Well Isn't That Special?" [umich.edu]

That said, I haven't read the current paper. They might have been very careful to avoid the common traps. I won't know until I spend some time tomorrow reading it.

• #### "junk science" of behavioral profiling (Score:5, Insightful)

on Tuesday January 17, 2012 @05:26AM (#38722500)

For behavioral profiling being a "junk science" they've had a lot of successes, and more success than this idea will ever yield (especially since it's so easily reverse engineerable, not to mention vague in its predictions). And the criticism coming from a criminal lawyer - well, I think the lady doth protest too much.

The basic idea of profiling is to narrow a large search down into a smaller one. The basis of the idea that by studying known offenders and finding commonalities between them, you'll have a clue as to the sort of person a perpetrator will be given an arbitrary new crime. Now that enough information about profiling is out there, offenders can and do reverse engineer the profiling process to make it tougher for them to get caught (assuming they are smart enough to do so - many are not that smart). However, at the very least there will be certain things that they are compelled to do otherwise the crime is simply not interesting for them to do. And certain things they have to do to carry out their crimes which will give a clue as to who they are.

The way I look at it, the people who study these particular criminals and offer advice for catching them are analogous to specialist doctors. For example, if you are trying to diagnose and treat some specialist skin condition that is very rare, you will have better results with a referral to a dermatologist than having the GP struggle and try to treat it as best he can.

• #### Re:Yeah I saw that on... (Score:2, Insightful)

on Tuesday January 17, 2012 @05:34AM (#38722532)

Many of us have better taste in TV.

• #### Just the data, ma'am, please.. (Score:5, Insightful)

<magnus AT freeshell DOT org> on Tuesday January 17, 2012 @05:44AM (#38722564) Homepage

Oh man, I get so bothered when someone presents interesting data - only to append a theory that isn't connected to it.
Why is that? Don't you get to publish unless you have a theory, no matter how unrelated an implausible it is?
Human sciences especially - it's understandable though, as it's hard to read people's minds.

Neurons firing? Really?? Does fantasizing about objects we can actually see and touch suddenly make it science?
If the study included brains scans or something, sure. But all they did was look at numbers.

If you don't have a theory that's related to your study, just post your data and spare us your fantasies. Thank you.

• #### Re:"junk science" of behavioral profiling (Score:5, Insightful)

on Tuesday January 17, 2012 @06:27AM (#38722718) Homepage

Actually, profiling has been seriously challenged, there's a nice New Yorker article [newyorker.com] about it, and several scholarly papers [anu.edu.au], Alison L and Rainbow L. eds (2011) 'Professionalizing Offender Profiling: Forensic and Investigative Psychology in Practice'. Routledge, London. The charge is that profiling is similar to astrology, make vague claims that could match a variety of scenarios, and pay attention when it fits, not when it doesn't.

Like a lot of forensic techniques, it seems to have jumped from the theoretically plausible to practice, without going through the intermediate step of check that it works. "Junk science" may be a fair characterisation.

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