Slashdot Mirror
Statisticians Uncover the Mathematics of a Serial Killer
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.'"
...is another series of murders to consolidate the theory.
Any takers?
Operation Guillotine is in effect.
Numb3rs already. Yawn.
Dear teeloo,
Many of us reside outside the US and/or have lives.
Sincerely,
The rest of /.
Il n'y a pas de Planet B.
Getting laid prevents serial killers? Suddenly I feel a lot less safe around here...
Sleeping with serial killers saves lives!
... but not necessarily yours...
Aren't they jumping the gun a bit?
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, you can find any pattern or picture in the stars if you look hard enough.
The 'murder probability' comes from a probability density function spanning three years, and is estimated from 53 data points, all from the same subject. That is hardly reliable.
And if we take the sparsity of the data for granted, what is the conclusion? That the less frequently the murderer acts, the less likely he is to act, and vice versa. It is a descriptive model, you can not predict the time of the next murder with it.
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.
You can never know everything, and part of what you do know will always be wrong. Perhaps even the most important part.
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".
Um, did you read anything on this guy? He couldn't get it up apparently, and that is what supposedly sent him into a rage. Dude was married, so ostensibly he had access to a woman, but if he couldn't get it up he couldn't get it up.....Not to mention you have killers like Ted Bundy who are incredibly charming(Bundy had something like 3 girlfriends at a time at some points in his life, dude even had women fawning over him AFTER they had learned he was a serial killer), but kill anyway......
Monstar L
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.
If I have seen further it is by stealing the Intellectual Property of giants.
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.
No sig to see here. Move along.
Many of us have torrents and like Us crime dramas without ads.:) (probably)
Buy Sky+ then. Oh, sorry, I forgot this is slashdot so we're entitled to anything we can get our hands on and believe that films and TV shows magically get made at no cost.
Yeah, blah blah "Intellectual property" doesn't really exist, it's only copying not stealing, whatever.
To have a right to do a thing is not at all the same as to be right in doing it
And in other news, police warn that the Sudoku killer will kill either 1, 4, or 9 victims next.
Here is the abstract of an article, "Power-Law distributions in empirical data" by Clauset et al (2009):
"Power-law distributions occur in many situations of scientific interest and have significant consequences for our understanding of natural and man-made phenomena. Unfortunately, the detection and characterization of power laws is complicated by the large fluctuations that occur in the tail of the distribution—the part of the distribution representing large but rare events— and by the difficulty of identifying the range over which power-law behavior holds. Commonly used methods for analyzing power-law data, such as least-squares fitting, can produce substantially inaccurate estimates of parameters for power-law distributions, and even in cases where such methods return accurate answers they are still unsatisfactory because they give no indication of whether the data obey a power law at all. Here we present a principled statistical framework for discerning and quantifying power-law behavior in empirical data. Our approach combines maximum-likelihood fitting methods with goodness-of-fit tests based on the Kolmogorov-Smirnov statistic and likelihood ratios. We evaluate the effectiveness of the approach with tests on synthetic data and give critical comparisons to previous approaches. We also apply the proposed methods to twenty-four real-world data sets from a range of different disciplines, each of which has been conjectured to follow a powerlaw distribution. In some cases we find these conjectures to be consistent with the data while in others the power law is ruled out."
So, I would recheck this guy's analysis.
And since the keyboard is mightier than the sword beware. I have a keyboard and I'm not afraid to use it.
You own an IBM Model M keyboard?
"Evil will always triumph because good is dumb." -- Dark Helmet
Yeah, blah blah "Intellectual property" doesn't really exist, it's only copying not stealing, whatever.
Unfortunate that you got modded troll, because you make a good point.
I have to ask, though - At what point do you consider time and/or format shifting as "piracy", for ethical purposes?
If I watch live TV, no piracy, ostensibly because we see the ads that "pay" for it. But I can (and back before TiVo, most people did) use commercials as food/bathroom breaks, or just flip channels during them, so even in the bad-ol'-days, no one really watched them.
If I buy the season on DVD, no piracy, because I've actually directly paid for the content.
If I download the same show from a torrent, most of us would agree that violates the spirit of copyright, even if we don't particularly care and do it anyway.
If I rent the DVD and rip it, I think most would consider that piracy.
And of course, we have the DVR, where I can time and format shift it to watch wherever and whenever I want, which IMO most people have come to accept as not piracy.
But - How does ripping or torrenting differ from the DVR case, either functionally or in terms of compensation? Whether I "rip" a show from broadcast TV or rip it from a DVD, it makes absolutely no difference to the producer. Whether I download it from a torrent or "download" it from my TiVo To Go, it makes absolutely no difference to the producer. Whether I watch it live and promise to completely ignore the commercials, or watch a torrented 4th-hand fansubbed unlocked-PSP version, it makes absolutely no difference to the producer.
Basically, once the producer has "given it away" by broadcasting it to the world, how can any use of that content really fall into the same box as "stealing"?
Some men are driven to drink, use drugs, post on slashdot in such situations. Others may be driven to commit homicide.
Some write Byzantine filesystems. Some do both.
You don't build a statistical model off of a single person.
Troll is not a replacement for I disagree.
Also, Superman doesn't really live in New York City,
We know that. He lives in Metropolis. Duh.
This is nice and all, but how many people need to be killed by a serial killer in order to get a sufficient data set to mathematically model his killing pattern?
Sorry, but, hand-waving at neurons to justify the power law they found is none the less also....
"relying on the junk science of behavioral profiling"