Justice Scalia
"Justice Breyer speculates that it does not 'seem likely' that the death penalty has a 'significant' deterrent effect," Supreme Court Justice Antonin Scalia
writes in his concurring opinion upholding Oklahoma's use of a drug used in a
gruesomely botched lethal injection. However, Scalia continues, "It seems very likely to me, and there are statistical studies that say so."
The thing is, there are more studies that say the death penalty is not a significant deterrent. Vox's German Lopez rounds up the research Scalia ignored:
The Death Penalty Information Center, one of the top nonpartisan sources for information about capital punishment, summarized a 2009 survey in which a large majority of criminologists said the death penalty isn't proven to deter homicides:
Eighty-eight percent of the country's top criminologists do not believe the death penalty acts as a deterrent to homicide, according to a new study published in the Journal of Criminal Law and Criminology and authored by Professor Michael Radelet, Chair of the Department of Sociology at the University of Colorado-Boulder, and Traci Lacock, also at Boulder.
The criminologists weren't talking about their personal beliefs, by the way. They were talking about their reading of the available research. But there's more:
A February 2015 review of the research by the Brennan Center for Justice found no evidence that the death penalty had an impact on crime in the 1990s and 2000s, and it concluded that the studies that suggested there was a deterrent effect were methodologically weak.
Not that we needed this to make the general point that we should aggressively question things Scalia believes are "very likely" true, but knowledge worth having.