What follows is an edited transcript of my conversation with Samuel Gross. Petersen: You're listening to Economics Detective Radio. My guest today is Samuel Gross of the University of Michigan Law School. Sam, welcome to Economics Detective Radio. Gross: Great to be here. Petersen: So our topic for today is criminal justice, in particular, we're going to be looking at the issue of wrongful conviction. Dr. Gross was part of the establishment of the National Registry of Exonerations which has provided valuable data in this area. So let's start by talking about the registry. What is it? How was it developed? And what was your part in it? Gross: I'm the founder of the registry. It was created because after doing work on false convictions and exonerations for half a dozen years it became clear that the only way to get any sort of systematic information on exonerations that have occurred in the United States would be to put together the wherewithal to collect that information directly because nobody else was doing it. There's no official system for gathering information on exonerations or for that matter a single legal definition of what is an exoneration. And from there this project just took off on its own and became what's now a lasting institution that's in the process of handing over to other people to run. Petersen: Okay, so let's talk about the how an exoneration is defined in the registry. It's a case where someone has been convicted and then later that conviction has been overturned and presumably not just on a technicality but because the person was actually innocent---somehow managed to prove their innocence. Is that correct? Gross: Something like that. The thing that we're interested in studying is false convictions. Convictions of people who are actually innocent. The problem is there's no way to know when that's happened directly because in cases where by assumption people have made errors, the juries and prosecutors and judges who considered the cases have made errors in deciding who is guilty and who is innocent. It would be foolhardy and presumptuous and not particularly accurate for us to believe that we're going to be better at deciding after the facts which cases involve those sorts of errors and which don't. So, what we've done instead---instead of trying to make any judgment of our own about guilt or innocence based on whatever information we can collect from second or third or fourth hand sources---what we do instead is to consider cases, to classify cases of exonerations if they meet the following criteria: First, the defendant has to have been convicted of a crime, not just charged, the conviction has to be completely removed. That is, at the end of the process the defendant has to have no legal consequences from the original conviction which means the conviction was entirely overturned by dismissal, or by a pardon, or in a small number of cases---or by the acquittal over retrial---or in a small number of cases by one of the few procedures that are available for people who are exonerated posthumously, after they're dead. And then in addition, the process that led to that result has to include substantial evidence of innocence that was not available at the time of the original conviction. If the case meets those criteria we include, if it doesn't we don't. Our belief is---and it's a hypothesis---is that this produces a conservative classification for actual innocence, for errors in determining guilt at trial. We know of quite a few cases of people who are very likely to be innocent who are not included by these criteria in particular. Quite a few cases of people who reach that result having the conviction entirely removed from the record without the production of new evidence of innocence. For example, cases in which the conviction was reversed and then they are dismissed want to appeal because there was insufficient evidence to convict at trial unless some other evidence comes up before the conviction is re