Monday, August 9, 2010

On The Rate of Wrongful Conviction: Chapter 5.4

As I have mentioned eight times previously, I am preparing a monograph on the rate of wrongful conviction. Each chapter will deal with one estimate of that rate, beginning with zero and ending beyond 10%. I am posting the draft chapters here, as I write them.  I have so far posted the following: 

Chapter 0.027: The Scalia Number
Chapter 0.5: The Huff Number
Chapter 0.8: The Prosecutor Number
Chapter 1.0: The Rosenbaum Number
Chapter 1.3: The Police Number
Chapter 1.4: The Poveda Number
Chapter 1.9: The Judge Number
Chapter 2.3: The Gross Number
Chapter 3.3: The Risinger Number

This post will be the last based on the Ramsey survey, the last based on a guess. After this post, we will move beyond those who survey and those who divide exonerations by convictions. Beginning with the next chapter, we will move into the more interesting world of judge-jury agreement.

Chapter 5.4
The Defense Number

The Ramsey Ohio survey study introduced in Chapter 0.8 was so comprehensive that it allows me to determine four separate wrongful conviction estimates: one each for prosecutors, police, judges, and defense attorneys. The prosecutors were the most conservative in their estimate, guessing that the wrongful conviction rate for the country is 0.8%.  The police were the next more conservative group, guessing that the wrongful conviction rate for the country is 1.3%. Then came the judges at 1.9%. Now it’s time to look at the defense attorneys.

Ramsey received responses from 216 defense attorneys. Their responses are categorized below.

Actually, 17 of the 22 public defenders I recorded in the 21% - 25% category estimated the rate was greater than 25%. I included them in the 21% - 25% category purely for convenience in plotting the results. It will cause the result to be slightly conservative, slightly low.

I'll define the Defense Number for the wrongful conviction rate in the same manner I defined the Prosecutor, Police, and Judge Numbers: I’ll determine the median guess at the wrongful conviction rate using a plot. That plot is presented below. Based on the plot, I claim the single best number to represent the wrongful conviction rate estimated by the Ohio private and public defense attorneys responding to the Ramsey survey is 5.4%.

Consider the significance of the Defense Number. If it is applicable to all 2.5 million people we have incarcerated, it suggests that even defense attorneys believe we have 125,000 people wrongfully incarcerated in this country today. As it turns out, the defense attorneys will have guessed more accurately than any of the other groups surveyed by Ramsey.


As mentioned in the earlier chapter dealing with the Ramsey survey, I noted that Ramsey was clever enough to ask for separate guesses of the wrongful conviction rate: one for the country as a whole and one for the respondent’s jurisdiction. It’s interesting to compare the two.

For the defense attorneys, the national median guess was 5.4%, as just reported. For that same group of attorneys, the median guess for their jurisdiction was 4.1%. On average, the defense attorneys believed the wrongful conviction rate in their jurisdiction was somewhat more than 75% that of the national average. This makes the defense attorneys the least delusion of the four groups, at least when considering the wrongful conviction rate in their jurisdiction relative to the nation as a whole.

For comparison, the numbers for the judges are 1.9% and 0.56%; that ratio is slightly less than 30%. The numbers for police are 1.3% and 0.2%; that ratio is slightly more than 15%. The numbers for prosecutors are 0.8% and 0.2%; that ratio is exactly 25%.


Ramsey was also clever enough to ask his respondents their opinion of an acceptable wrongful conviction rate. Slightly more than half the judges and police felt the acceptable rate was zero. Slightly fewer than half the prosecutors felt the acceptable rate was zero. Fifty-two percent of the defense attorneys thought the acceptable rate was zero. With respect to this median value, the four groups are in agreement.

Good for all of them. While no one is arguing a zero rate is achievable, it’s good that half of all police, prosecutors, and judges feel a wrongful conviction is an unacceptable circumstance. Perhaps they would be willing to help free some of the 20 to 125 thousand people they believe are now wrongfully imprisoned.

At the other extreme, one prosecutor, four judges and five defense attorneys thought 5% would be an acceptable wrongful conviction rate.

Three police respondents also thought 5% was an acceptably-low wrongful conviction rate. Four police respondents thought 10% would be acceptable. Two of them thought 15% would be okay. Astoundingly, one police respondent thought that a wrongful conviction rate of 20% was not too high.

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