Another important number is, those less than 10% who do, how many more people they kill?
Imagine that you have nine murderers who kill 1 person each, and one serial killer who kills 100. It is simultaneously true that only 10% murderers murder again and that executing them could save many lives. (But a life in prison, if the chances of escape are sufficiently low, could achieve the same.)
Fair statistical point, however in reality a vast majority of serial killers did not go above 15 victims, and the crimes they commited were perpretated before their first (and last) arrest. I do not have raw numbers, but my impression is that the number of those sentenced for one murder, later paroled, and then beginning their spree of more than 3-4, is incredibly small. Serial killers are also rare in general.
Gang considerations, however, might be a larger factor here, though I still doubt it is enough to tip the scales (especially as prison gang affiliation is a factor taken into account when considering parole). 13% of homicides are gang-related, though gang members are twice as likely to re-offend (both for violent offences and not). Even if we (awkwardly) extrapolate twice as likely to re-offend to twice as many murders after parole, this still does not meaningfully change the ball-park figures.
If we have 80 murderers, of which 10 are gang members, which are released (with gang members less likely to be released, mind, so this is an over-estimation), then we would have 7 homicidal recidivists and 1 homicidal gang recidivist, who commits two crimes instead of 1. Instead of 8 murders, we have 9: 12.5% remurdering instead of 10%, at most. I have fudged the numbers, but I don’t think this substantially changes what I have said.
Another important number is, those less than 10% who do, how many more people they kill?
Imagine that you have nine murderers who kill 1 person each, and one serial killer who kills 100. It is simultaneously true that only 10% murderers murder again and that executing them could save many lives. (But a life in prison, if the chances of escape are sufficiently low, could achieve the same.)
Fair statistical point, however in reality a vast majority of serial killers did not go above 15 victims, and the crimes they commited were perpretated before their first (and last) arrest. I do not have raw numbers, but my impression is that the number of those sentenced for one murder, later paroled, and then beginning their spree of more than 3-4, is incredibly small. Serial killers are also rare in general.
Gang considerations, however, might be a larger factor here, though I still doubt it is enough to tip the scales (especially as prison gang affiliation is a factor taken into account when considering parole). 13% of homicides are gang-related, though gang members are twice as likely to re-offend (both for violent offences and not). Even if we (awkwardly) extrapolate twice as likely to re-offend to twice as many murders after parole, this still does not meaningfully change the ball-park figures.
If we have 80 murderers, of which 10 are gang members, which are released (with gang members less likely to be released, mind, so this is an over-estimation), then we would have 7 homicidal recidivists and 1 homicidal gang recidivist, who commits two crimes instead of 1. Instead of 8 murders, we have 9: 12.5% remurdering instead of 10%, at most. I have fudged the numbers, but I don’t think this substantially changes what I have said.