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This article from New Scientist asks whether sleep walkers can be held morally responsible for acts committed while unconscious. A different question is what effect a sleepwalker exception would have on crime. Would it encourage sleepwalkers to commit more crimes, or on the extensive margin would it encourage more to people to take up sleepwalking?
I have no personal experience, but if sleepwalkers believe they are awake, then they would not be motivated by an exemption for sleepwalkers. Of course at any moment in time all of us may be sleepwalking and assuming we all account for that small probability, a sleepwalker exemption would encourage more crime across the board. This could be easily compensated by a small, uniform increase in penalties.
We shold worry that non-sleepwalkers will make use of the additional defense at trial (the “jammie defense?”)
Nightcap Nod: Mindhacks.
My mother tells me that where she lives there are cameras that will catch you if you don’t come to a complete stop at the octagonal sign. Your license plates will be photographed and you will be sent a bill in the mail. The fine is close to $500. That’s a lot more than I remember it.
Quiz: suppose the technology improves for detecting whether a violation has taken place. Should the fine increase, decrease or stay constant?
Steve Levitt links to his paper with Sudhir Venkatesh documenting some stylized facts about street prostitution in Chicago. It’s definitely worth a read, and one part is fodder for theory:
Prostitutes in their sample report using condoms 90 percent of the time, compared to only 25 percent in our sample for vaginal sex, and 21 percent for anal sex. Among their Mexican prostitutes, condom use is the default from which customers must bargain away, potentially inducing large increases in prices. In contrast, in our sample no condom appears to be the default choice, perhaps making it harder for the prostitute to credibly argue for a higher price if no condom is used. Moreover, in an equilibrium in which condom use is infrequent, infection rates among prostitutes are likely to be extremely high, so that the primary value of condoms to women may be protecting the women from becoming pregnant and hygiene, rather than the spread of disease. Indeed, one would expect that the johns would likely gain more in disease reduction from condoms than the prostitutes.
SOME DISCUSSION OF HOW CONDOM USE VARIES ACROSS PROSTITUTES IN OUR SAMPLE. SOME QUOTES ABOUT WHY THEY DON’T USE THEM. SOME FACTS ABOUT AIDS RATES AMONG JOHNS AND PROSTITUTES FROM MEDICAL LITERATURE.
(hmmm, it appears they are not quite done with the paper 
) They focus on the cost to the prostitute due to increased infection and the like, but there is already some unusual aspects to the demand side.
A John values unprotected sex over protected sex but even moreso if he is the only John, or among very few, who get that privelege. Holding fixed her frequency of unprotected sex, there is a downward sloping demand for unprotected sex as a function of the price premium over condom-clad. But that frequency is not verifiable, except insofar as it can be inferred from the price. Thus, as an equilibrium response the demand curve itself shifts with adjustments to the price.
This means that the prostitute cannot just choose any price. The price must be such that x% of Johns are willing to pay that price when they assume that x% of other Johns are having unprotected sex. Typically there will be just a few values of x that satisfy this fixed-point relationship.
So a cross-section of pricing patterns will exhibit a bang-bang (quiet down Beavis) or bi-modal (Beavis!) histogram with high prices and low prices and none in-between. The high prices correspond to the equlibria in which few Johns have unprotected sex so Johns are willing to pay a lot, and the low prices correspond to the equilibria in which many Johns have unprotected sex and Johns place lower value on it.
It could even happen that the price premium is for protected sex. In fact it could even be profit maximizing to distort downward the price of unprotected sex in order to signal how risky that would be, enabling the prostitute to raise the price of protected sex.
Should punishment depreciate as time passes? As usual the answer probably depends on whether you think of punishment as justice or as a mechanism to internalize externalities.
I can see how the demands of justice could be reduced and even expire after many years pass. One view is that identity evolves and eventually the accused is a different person from the criminal of the past and justice is not served by punishing someone who is effectively a third party.
On the other hand, if the purpose is to deter crime then the passage of time should arguably increase the punishment. What matters is the perceived cost of the act evaluated at the time of acting. A fixed penalty (possibly) deferred far in the future imposes a smaller cost. To compensate for the discounting, the size of the penalty must be larger when it begins later. Its tempting to say that because the time for acting has already passed there is no retroactive incentive effect from extending the punishment. But this logic would undermine all penalties after the fact. Indeed, the incentive theory of punishment relies on prosecutors holding to their commitments presumably because of reputational concerns.
Working against this is the incentive effect on prosecutors. One reading of a statute of limitations is that it compels prosecutors to make reasonably prompt decisions to bring charges. We can model this by supposing there is a flow cost of maintaining a defense: keeping track of the whereabouts of witnesses, preserving documents, coordinating the memories of all involved. The freedom to delay induces prosecutors to optimally impose costs on the innocent in order to maximize chances of conviction.
Presumably the latter is less of a concern when the criminal has already confessed.
Suppose that a plane has just landed and a flu pandemic may be emerging. You have the time and resources to check some but not all of the arriving passengers for signs of influenza. A small fraction of the passengers are arriving from Mexico where the pandemic originated and the others have not been to Mexico. How do you allocate your searches?
Efficient screening means that the probability of finding an infected passenger should be equalized across the groups that you screen. And if searches of one group yield a higher infection rate than another then you should allocate your searches to the first group. Since the passengers arriving from Mexico are much more likely to be infected, you will probably use all of your searches on them.
Even though the passengers from Mexico are being searched disproportionally more often than the others, this is not because you are discriminating against them. Your motive is simply to use your limited resources most effectively to stop the spread of the virus.
These ideas should be kept in mind when you read articles like this one (via The Browser) which claim that the disproportionate number of searches of black motorists on the highways indicates that the police are racially biased. The police probably are racists, this would not surprise anybody. But the fact that they stop and search black motorists more often than whites is not evidence of racism, unless it can be shown that the proportion of stopped black motorists who are found to be committing a crime is smaller than the proportion of stopped white motorists.
In fact, this 2001 paper by Knowles, Persico, and Todd test for this using one particualar data set and find no evidence of bias. I don’t know where the literature has gone since then, probably there have been other studies with other findings, but its important to know what the right test is.
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