Sentencing and Conventional Number Preferences: A Research Note

Published date01 June 2006
Date01 June 2006
Subject MatterArticle
Sentencing and Conventional Number Preferences • 67
* Sentencing and Conventional Number
Preferences: A Research Note
Andrew Wiseman
Daniel Fischer
Michael Connelly
Wisconsin Sentencing Commission
* Abstract
Prior research on sentencing has shown that judges rely heavily on “conventional
number preferences” (CNPs), often defaulting to certain “preferred” sentences, e.g.,
three years, four years, ve years, etc., that come easily to mind. Data from Wiscon-
sin conrm that its judges, virtually unbound in their discretion, are likewise heavily
inuenced by CNPs, with 10 prominent sentences explaining almost all non-proba-
tion felony sentences. Wisconsin currently spends nearly $2,300 per prisoner, per
month. Strong preferences for three-, four-, and ve-year sentences, when shorter
terms would sufce, cost the state millions of dollars each year. Additionally, CNPs
may result in disproportionate sentences for offenders who commit the same crime.
This paper was funded in part by a grant from the National Institute of Justice (NIJ).
The authors thank their anonymous reviewers at Justice Research and Policy for their
careful reading and thoughtful recommendations. The authors also thank the Honorable
Thomas H. Barland, Eau Claire County Circuit Court (emeritus), who provided valuable
insight into the ndings reported here.
© 2006 Justice Research and Statistics Association
68 • Justice Research and Policy
Sentencing and Conventional Number Preferences • 69
* Introduction
Since the 19th century, researchers have documented strong preferences among
judges for particular criminal sentences—terms that correspond with whole,
often round, numbers. In 1895, Francis Galton observed,
The terms of imprisonment that are most frequently awarded fall into
rhythmic series. Beginning with sentences reckoned in months, we see
that their maxima of frequency are at 3, 6, 9, 12, 15 and 18 months,
which are separated from one another by the uniform interval of 3
months . . . a round gure that must commend itself to the judge by its
simplicity (p. 175).
A century later, Ostrom and Ostrom (2002) observed the same phenomenon:
Actual sentence length may not be consistent with a continuous “scale
of severity.” Consider the distribution of prison sentences among 9,586
offenders convicted in the State of Michigan in 1995. Prison sentences
range from one month to 480 months. Michigan judges are free to as-
sign any term of days, months or years they wish. However, it is clear
that a small number of sentences predominate: 12, 18, 20, 24, 30, 36,
48, 60, 72, 84, 96 and 120 months. These 10 [sic] terms account for
over 78 percent of sentences issued in 1995 (p. 277).
As the Ostroms contend, profound policy consequences follow from observed
judicial preferences for particular sentences: public safety demands that offenders
receive their just deserts, but prisoners suffer unduly, and we squander scarce, ex-
pensive prison space if our afnity for particular numbers leads to sentences that
exceed just penal deserts (pp. 279–280). Essentially, the Ostroms’ ndings con-
rm what Fitzmaurice and Pease (1986) had stated years before—that judges increase
sentence length apace with what they perceive inexactly as greater culpability.
The Ostroms maintain that the policy implications of conventional num-
ber preferences (CNPs) are three. First, strong preferences for certain numbers
may result in disproportionate sentences—12 years vs. 15, or 15 vs. 20—for
similar offenders who commit the same crimes. Second, this inconsistency can
easily become racial disparity if judges consistently impose longer sentences on
minorities. And third, coupled with rising pressure to increase sentence length,
conventional number preferences put heavy pressure on available prison space.
These effects can have profound consequences anywhere. This research note
attempts to replicate the Ostroms’ ndings in Wisconsin, and raises additional
implications that follow from our analysis.
* Literature Review
As noted above, scholars have found that actual sentence length does not co-
incide with a continuous scale of severity. Ostrom and Ostrom (2002) offer
68 • Justice Research and Policy
Sentencing and Conventional Number Preferences • 69
three explanations for the appearance of CNPs among sentencing judges. First,
a restricted choice set reects the human tendency to simplify complex deci-
sions—judges proceed toward the “right” sentence from several options that
are “good enough.” This accords with Farrell and Holmes (1991), and Guthrie,
Rachlinsky and Wistrich (2001), who maintain that judges use mental shortcuts,
including stereotyping, framing, hindsight bias, and anchoring (making nal de-
terminations based on arbitrary starting points) to solve complex problems. Ac-
cording to Farrell and Holmes (1991), while these “tools” may facilitate sound
decision-making, they often produce cognitive illusions that systematically yield
erroneous sentences:
Alleged perpetrators of violent and property crimes, for example, are
likely dealt with more severely if their alternative statuses conform to
lower class and minority group stereotypes popularly associated with
such offenses. More severe treatment may be deemed necessary to in-
capacitate offenders whose behavior is thought deeply rooted in their
social backgrounds, [and] thus likely to reoccur.
. . .
Wheeler and his associates (1982) nd a strong relationship between
white-collar offenders’ occupational status and probability of impris-
onment. Contradicting popular and social scientic opinion, their data
show that offenders of higher occupational status are more likely to
ceive prison sentences than lower status, “run of the mill” offenders. . . .
Held more responsible, defendants of higher social status are perceived
[to be] exceptional and their deviation more serious, warranting more
severe penalties (pp. 534–535).
Second, when reducing their choice set, judges default to sentences that are
easily recalled. Ostrom and Ostrom (2002) suggest that this process may illus-
trate what Kahneman, Slovic and Tversky (1982) have termed the “availability”
heuristic. The availability heuristic leads to several decision-making biases, chief
among them being that judges in discretionary environments will most frequent-
ly impose those few “prominent” sentences that come easily to mind. Dhami
(2005) and Dhami and Ayton (2001) have similarly reported that the decision-
making process in bail decisions in the United Kingdom is less complicated than
one might imagine:
[P]sychological research has examined the cognitive processes involved in
making bail decisions (Dhami 2003; Dhami & Ayton 2001). It has been
found that the decisions of both judges responding to simulated cases
and judges responding to real cases in the courtroom are better predicted
by a simple heuristic called the matching heuristic than by more complex
strategies. According to the heuristic, judges search through only a small
subset of the available case information, and then base their decision on
the level of one factor alone (Dhami, 2005, p. 371).

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