Criminologist questions AZ prison study results

January 11, 2012

A criminologist questions the conclusions reached by a study done for the Arizona Prosecuting Attorneys Advisory Council.  It found Arizona sentencing laws are preventing crime and saving money.  But a law professor at the University of California-Berkeley says the data doesn’t necessarily support that conclusion.  From Phoenix, KJZZ’s Paul Atkinson reports.

Arizona Inmate Population Crime Type, 1985-2010

Type Inmates Percentage
Property Crime85,43429%
Violent Crime64,47622%
Drug Possession36,20912%
Drug Trafficking33,98612%
Sex Crime12,2244%

Source: Arizona Prosecuting Attorneys' Advisory Council

Maricopa County Attorney Bill Montgomery

Franklin Zimring

The Arizona Prosecuting Attorneys Advisory Council commissioned the 515-page study. Yavapai County Attorney Sheila Polk says she and other prosecutors were fed up with sentencing reform proposals that lacked hard data. 

SHEILA POLK “we want to know who is in our prisons, why they are there, and is there any correlation between truth in sentencing and the crime rate?”

Polk says the study found -- that of the 40-thousand inmates now in state prison –69-percent are violent offenders.  26-percent are non-violent repeat offenders, and five-percent are non-violent first time offenders.

More importantly, the study shows that crime peaked in Arizona in 2001, and dropped more than 38-percent since then.   Polk says the research also found that fewer people are now being sent to prison.

SHEILA POLK “The fact that our crime rate is falling as our prison population is falling as our prison population is falling, again says that we are locking up the right people.”

The study also examined the impact of Arizona’s truth-in-sentencing laws -- which require inmates to serve 85-percent of their prison sentence before being eligible for release.  Maricopa County Attorney Bill Montgomery says when risk factors such as past drug use and gang membership are taken into account, truth-in-sentencing laws proved effective in preventing more crime.

BILL MONTGOMERY  “When we looked at the difference between the terms of sentences before truth in sentencing was passed in 1994 and after truth in sentencing was passed, we found that when you hold those risk factors constant – inmates who served 85-percent of their sentences on average were between 2 and 3 percent less likely to reoffend than the general population.”

FRANKLIN ZIMRING  “Incapacitation studies begin as a statistical guessing game.”

Criminologist and University of California Berkeley law professor Franklin Zimring says the methodology used in the Arizona inmate study is relatively cautious.  But he warns that the conclusions reached on the impact of truth-in-sentencing laws are flawed.  Zimring says there is a high margin of error rate in predicting what inmates will reoffend. 

FRANKLIN ZIMRING “To think that you can slice these statistical guesses that thinly and that precisely without any kind of control group requires a kind of optimism which seems to infect prosecutors far more often than it infects criminologists.”

Zimring says the higher cost of incarceration should have been calculated and compared to the 200-million dollars in savings the study found from keeping criminals off the streets.  Still, the criminologist finds the data in the study of Arizona prison inmates a good starting point for discussing effective crime prevention policies. 

Link to the study: PRISONERS IN ARIZONA: Truth-in-Sentencing, Time Served and Recidivism