A new study published in the Proceedings of the National Academy of Sciences, one of the world’s most prestigious scientific journals, asserts that 4.1% of the people now on death row would be exonerated if they stayed on death row indefinitely. There have, in fact, been 143 death row exonerations since 1973, when the modern death penalty was authorized by the United States Supreme Court. Through 2004, the rate of exoneration for death-row inmates was 2.3%. The authors point out that as a general matter, it is difficult to determine the error rate in the criminal justice system since if a person is known to be innocent at the time of conviction, he should not be convicted in the first place. But death sentences, which are only a minuscule fraction of overall convictions, get much more attention than other cases, resulting in a higher rate of exoneration. The authors consider the 4.1% error rate a conservative number — the real number of false death penalty convictions is probably higher. The real number of false convictions overall is probably higher still. The article, Rate of False Conviction of Criminal Defendants who are Sentenced to Death, was co-authored by several scholars, including Samuel Gross, a University of Michigan law professor who is the editor of the National Registry of Exonerations, which tracks exonerations in the United States.