Title: State v. Frank Curiel
Citation: N/A
Docket Number: 1997AP001337
State: Wisconsin
Issuer: Wisconsin Supreme Court
Date: July 2, 1999

SUPREME COURT OF WISCONSIN 
 
 
Case No.: 
97-1337 
 
 
Complete Title 
of Case: 
 
 
In re the Commitment of Frank Curiel: 
 
State of Wisconsin,  
 
Petitioner-Respondent, 
 
v. 
Frank Curiel,  
 
Respondent-Appellant-Petitioner.  
 
ON REVIEW OF A DECISION OF THE COURT OF APPEALS 
Reported at:  221 Wis. 2d 596, 586 N.W.2d 698 
 
 
 
(Ct. App. 1998, Unpublished) 
 
 
Opinion Filed: 
July 2, 1999 
Submitted on Briefs: 
 
Oral Argument: 
May 4, 1999 
 
 
Source of APPEAL 
 
COURT: 
Circuit 
 
COUNTY: 
Milwaukee 
 
JUDGE: 
Jeffrey A. Kremers  
 
 
JUSTICES: 
 
Concurred: 
 
 
Dissented: 
 
 
Not Participating: Prosser, J., did not participate. 
 
 
ATTORNEYS: 
For the respondent-appellant-petitioner there 
were briefs by Jack C. Hoag and Sedor & Hoag, Janesville and oral 
argument by Jack C. Hoag. 
 
 
For the petitioner-respondent the cause was 
argued by Sally L. Wellman, assistant attorney general, with whom 
on the brief was James E. Doyle, attorney general. 
 
No. 
97-1337 
 
1 
 
NOTICE 
This opinion is subject to further editing and 
modification.  The final version will appear in 
the bound volume of the official reports. 
 
 
No. 97-1337 
 
STATE OF WISCONSIN               :        
        
 
 
 
 
IN SUPREME COURT 
 
 
In re the Commitment of Frank Curiel: 
 
State of Wisconsin,  
 
          Petitioner-Respondent, 
 
     v. 
 
Frank Curiel,  
 
          Respondent-Appellant-Petitioner.  
FILED 
 
JUL 2, 1999 
 
Marilyn L. Graves 
Clerk of Supreme Court 
Madison, WI 
 
 
 
 
REVIEW of a decision of the Court of Appeals.  Affirmed. 
¶1 
DONALD 
W. 
STEINMETZ, 
J.   The 
petitioner, 
Frank 
Curiel, seeks review of an unpublished decision of the court of 
appeals1 which upheld a verdict and commitment order of the 
Circuit Court for Milwaukee County, the Honorable Jeffrey A. 
Kremers.  The circuit court found Curiel to be a sexually 
violent person under Wis. Stat. ch. 980 (1995-96)2 and ordered 
his commitment. 
¶2 
We are presented with the following issues for our 
review: 
                     
1 State v. Curiel, No. 97-1337, unpublished slip op. (Ct. 
App. July 21, 1998).  
2 All future statutory references are to the 1995-96 volume 
unless otherwise indicated.  
No. 
97-1337 
 
2 
¶3 
1) 
What 
is 
the 
proper 
interpretation 
of 
"substantially probable" as the term is used in Wis. Stat. ch. 
980?  We hold that "substantially probable," construed according 
to its common and appropriate usage, means "much more likely 
than not." 
¶4 
2)  Is a person's right to equal protection violated 
where a finding of dangerousness under Wis. Stat. ch. 980 does 
not require that the risk that the person will engage in sexual 
violence is to a degree of "extreme likelihood?"  We hold that 
the standards for dangerousness under ch. 980 do not violate 
equal protection. 
¶5 
3)  Is the term "substantially probable" as used to 
determine whether a defendant is dangerous under Wis. Stat. ch. 
980 
unconstitutionally 
vague? 
 
We 
hold 
that 
the 
term 
"substantially probable," when construed according to its common 
and appropriate usage to mean "much more likely than not," is 
not unconstitutionally vague. 
¶6 
4) 
Whether the proper standard of review to apply to 
a challenge to the sufficiency of the evidence in a Wis. Stat. 
ch. 980 proceeding is that used in criminal or civil cases.  We 
hold 
that 
appellate 
court 
review 
of 
challenges 
to 
the 
sufficiency of the evidence in ch. 980 proceedings should be 
that standard applied in criminal cases. 
¶7 
5)  Is the verdict of the court supported by the 
evidence?  We hold that the evidence adduced at trial was 
sufficient to support the commitment of the defendant under Wis. 
Stat. ch. 980. 
No. 
97-1337 
 
3 
I 
¶8 
In 1989, Frank Curiel (Curiel) was convicted of second 
degree sexual assault in violation of Wis. Stat. § 940.225(2)(e) 
(1985-86) and was sentenced to prison for a term of six years.  
Prior to his scheduled release, the State petitioned for his 
commitment under ch. 980, which governs the civil commitment of 
sexually violent persons.  The State satisfied the circuit court 
that Curiel was eligible for commitment and, following a number 
of adjournments, a trial to the court was held on December 2, 
1996.3 
¶9 
The only disputed issue at trial was whether it was 
substantially probable that Curiel would engage in future acts 
of sexual violence.4  Both witnesses for the State testified 
that, to a reasonable degree of psychological certainty, it was 
substantially probable that Curiel would engage in future acts 
of sexual violence.  The one witness for the defense testified 
that it was not.  None of the witnesses, however, used the same 
                     
3  Curiel waived his statutory right to a jury trial. 
4 Under Wis. Stat. § 980.05(3)(a), the State has the burden 
of proving beyond a reasonable doubt all of the allegations in 
the petition for commitment.  The petition "must allege that the 
person:  (1) was convicted, found delinquent, or found not 
guilty by reason of mental disease or defect of a sexually 
violent offense; (2) is within 90 days of release from a 
sentence, commitment, or secured correctional facility arising 
from a sexually violent offense; (3) has a mental disorder; and 
(4) is dangerous because that mental disorder creates a 
substantial probability that he or she will engage in acts of 
sexual violence."  State v. Post, 197 Wis. 2d 279, 297-98, 541 
N.W.2d 115 (1995) (footnotes omitted); Wis. Stat. § 980.02(2).   
No. 
97-1337 
 
4 
working definition of "substantially probable" in reaching their 
conclusions. 
¶10 The State called Dr. Frederick Waddell (Waddell), a 
psychologist with the Kettle Moraine Correctional Institution, 
as its first witness.  Waddell testified that he had concluded 
to a reasonable degree of psychological certainty that Curiel 
suffered from the mental disorder known as pedophilia and that 
it was substantially probable that because of the disorder 
Curiel would engage in future acts of sexual violence.  He 
explained that he reached these conclusions based upon an 
approximately one hour interview with Curiel and an examination 
of Curiel's social services and clinical services files, which 
included a copy of Curiel's presentence investigation report.  
He based his conclusion that it was substantially probable that 
Curiel would reoffend sexually on the following five factors: 1) 
Curiel 
was 
diagnosed 
a 
pedophile, 
2) 
had 
episodes 
of 
exhibitionism, 3) was not treated for either pedophilia or 
exhibitionism, 4) had serious problems with drugs and alcohol, 
and 5) his known sexual offenses demonstrated a pattern of 
increasing severity.  Waddell also testified that his personal 
working definition of "substantially probable" was "more likely 
than not" and that he did not think it was "substantially 
probable" that Curiel would engage in future acts of sexual 
violence if that term were defined as "much more likely than 
not."  Following his testimony, his written evaluation of Curiel 
was admitted into evidence. 
No. 
97-1337 
 
5 
¶11 As its second witness, the State called Dr. Ronald 
Sindberg (Sindberg), a psychologist employed by the Mendota 
Mental Health Institute.  As did Waddell, Sindberg testified to 
a reasonable degree of psychological certainty that Curiel had a 
mental 
disorder 
known 
as 
pedophilia 
and 
that 
it 
was 
substantially probable that Curiel would engage in future acts 
of sexual 
violence.  He 
based his 
conclusion upon his 
examination of Curiel's social services and clinical files; 
Curiel, on the advice of his attorney, refused to speak with 
Sindberg. 
Sindberg's opinion 
was 
developed 
by 
considering 
whether Curiel met the criteria for a number of risk factors 
used to predict whether a person was likely to reoffend 
sexually, and then whether treatment that Curiel had received 
would tend to diminish the weight of the risk factors. 
¶12 Specifically, Sindberg testified that Curiel met the 
criteria for 17 of 31 risk factors the Mendota Mental Health 
Institute had identified as predictors that a person would 
commit future acts of sexual violence.  He further testified 
that of those 31 risk factors, 14 were regarded in scientific 
literature as highly reliable predictors of future acts of 
sexual violence.  Of those 14 most reliable risk factors, 
Sindberg found that Curiel met the criteria for the following 
ten: 1) pretreatment deviate sexual arousal, 2) non-sexual 
criminality, 3) denial or minimization of offenses, 4) extra 
familial 
victims, 
5) 
never 
very 
married, 
6) 
multiple 
paraphilias, 7) attitudes which legitimize crimes, 8) hands on 
and hands off offenses, 9) history of sexual abuse as a child, 
No. 
97-1337 
 
6 
and 10) history of substance abuse.  Sindberg testified that 
together, these risk factors made it substantially probable that 
Curiel would reoffend.  He stated that he did not believe that 
the non-sex offender treatment Curiel had received offset to any 
significant degree the weight of these risk factors.  Finally, 
he explained that his opinion remained the same whether 
"substantially probable" was defined as "more likely than not" 
or "much more likely than not."  Sindberg's written evaluation 
was also admitted into evidence. 
¶13 At the close of the State's case, defense counsel 
moved for a directed verdict, arguing that the evidence was 
insufficient 
to 
establish 
that 
there 
was 
a 
substantial 
probability that Curiel would reoffend.  Defense counsel argued 
first that Sindberg's testimony could not support a finding that 
the risk that Curiel would reoffend sexually was substantially 
probable because Sindberg's method of evaluation was fraught 
with error: he did not personally interview Curiel and in the 
view of the defense, his use of objectively-based risk factors 
to reach his conclusion was a questionable method of evaluation. 
 Then, with the premise that the term "substantially probable" 
must mean a degree of likelihood no less probable than "much 
more likely than not," counsel argued that Waddell's testimony 
was insufficient to support a finding of "dangerousness." 
¶14 The circuit court denied the motion.  It found that 
regardless of the fact that the witnesses used varied working 
definitions of the term, both had testified that it was 
substantially probable that Curiel would reoffend.  Second, the 
No. 
97-1337 
 
7 
court stated that even if "substantially probable" were defined 
as "much more likely than not," that standard was satisfied by 
Sindberg's testimony alone. 
¶15 The defense called a single witness in rebuttal, Dr. 
Charles Lodl (Lodl), a psychologist in private practice.  Lodl 
testified that he had met with Curiel for many hours and that he 
performed three psychological tests, including two that were 
directed 
toward 
assessing 
Curiel's 
sexual 
interests 
and 
knowledge. 
 
Lodl 
further 
testified 
that 
based 
on 
this 
background, 
and 
to 
a 
reasonable 
degree 
of 
psychological 
certainty, it was not substantially probable that Curiel would 
engage in future acts of sexual violence.  He had concluded that 
Curiel was a moderate risk for reoffending sexually.  He also 
testified that he internalized the probability of future acts of 
sexual violence as a five-point scale that he described as "low 
risk," "low to moderate risk," "moderate risk," "moderate to 
high risk," and "high risk."  He believed only "moderate to high 
risk" and "high risk" equated with the term "substantially 
probable." 
¶16 Lodl also cast doubt on the analysis Sindberg used in 
developing his expert opinion.  Of the 14 factors which Sindberg 
had claimed most accurately predicted whether a person would 
engage in a future act of sexual violence, Lodl admitted that 
scientific literature had once given its support; however, some 
of the factors more recently had been called into doubt as less 
predicative of such behavior than once thought.  He further 
testified that one's consideration of all the risk factors 
No. 
97-1337 
 
8 
should not be conducted in a "check-mark" manner but should 
include some clinical judgment that was based in part on an 
interview with the subject. 
¶17 Considering the evidence before it, the circuit court 
believed that the State had carried its burden to prove all the 
allegations in the petition for commitment beyond a reasonable 
doubt.  As relevant to its decision on the disputed question of 
whether it was substantially probable that Curiel would engage 
in future acts of sexual violence, the circuit court expressed 
its reasoning as follows: 
 
Now what I have then is someone who, according to 
everybody, including Dr. Lodl, is at a high risk of 
reoffending criminally, is at a moderate risk of 
reoffending sexually, if you look at Dr. Lodl's 
conclusions, at a much more likely than not risk if 
you listen to Dr. Sindberg and more likely than not if 
you listen to Dr. Waddell.  Under any standard that I 
thinkifif the standard that's in chapter 980 is 
constitutional, 
then 
this 
evidence 
in 
my 
mind 
establishes beyond a reasonable doubt that Mr. Curiel 
as he presently carries himself and views himself and 
deals with his psychological problems is dangerous as 
that term is defined in chapter 980, and I am finding 
that 
the 
State 
has 
proved 
this 
case 
beyond 
a 
reasonable doubt, and I find that Mr. Curiel is a 
sexually violent person as alleged in the petition. 
The circuit court then committed Curiel to the custody of the 
Department of Health and Social Services for control. 
¶18 The court of appeals affirmed the circuit court's 
verdict and commitment order.  It concluded that the term 
"substantially probable" required no further definition as the 
legislature 
intended 
the 
phrase 
to 
mean 
"substantially 
probable."  State v. Curiel, No. 97-1337, unpublished slip op. 
No. 
97-1337 
 
9 
at 8 (Ct. App. July 21, 1998).  It also concluded that Waddell's 
and Sindberg's testimony served as sufficient evidence to 
support the circuit court's findings that Curiel was dangerous. 
 Id. at 8-9.  As one point of error, Curiel had also appealed 
the circuit court's finding that Lodl had testified that Curiel 
was "at a high risk of reoffending criminally."  The court of 
appeals 
believed 
that 
the 
circuit 
court's 
statement 
was 
inconsequential to its decision and was nonetheless immediately 
followed by accurate facts upon which its decision was based.  
Id. at 9. 
¶19 We affirm the decision of the court of appeals but 
disagree that the term “substantially probable” needs no further 
definition.  We conclude that when the legislature used 
"substantially probable," it intended that the standard be read 
according to its common and appropriate usage: "much more likely 
than not." 
II 
¶20 On appeal to this court, in addition to the issues 
presented in the court of appeals, Curiel for the first time 
challenges the constitutionality of ch. 980.  The constitutional 
challenges 
Curiel 
makes 
here 
are 
also 
presented 
by 
the 
petitioner Peter Kienitz (Kienitz) in the companion case State 
v. Kienitz, No. 97-1460, filed this same date.  Those statutory 
and constitutional challenges made by both Curiel and Kienitz 
are addressed here. 
¶21 Lying at the heart of each of Curiel's arguments on 
appeal is the meaning of "substantially probable" as that term 
No. 
97-1337 
 
10
is used in ch. 980.  First, Curiel argues that "substantially 
probable" means "extreme likelihood" and that the circuit court 
erred in failing to so define the term.  Second, Curiel argues 
that the failure to define "substantially probable" as meaning 
"extreme likelihood" violates his right to equal protection.  
Third, Curiel argues that the court of appeals' failure to 
further 
define 
"substantially 
probable" 
leaves 
ch. 
980 
unconstitutionally vague.  And finally, Curiel asserts that the 
evidence adduced at his commitment trial was insufficient to 
support a finding that to the degree required by statute, he 
would engage in future acts of sexual violence. 
Statutory Interpretation 
¶22 Our analysis appropriately begins with determining the 
meaning of "substantially probable" as the term is used in ch. 
980.  Under Wis. Stat. § 980.01(7), a person "is dangerous 
because he or she suffers from a mental disorder that makes it 
substantially probable that the person will engage in acts of 
sexual violence." Id. (emphasis supplied).  Pursuant to Wis. 
Stat. § 980.02(2)(c), the State must prove beyond a reasonable 
doubt that "[t]he person is dangerous to others because the 
person's mental disorder creates a substantial probability that 
he or she will engage in acts of sexual violence."  Id. 
(emphasis supplied).  We explicitly note this difference in the 
phrasing of the term to emphasize that our interpretation of 
"substantially probable" serves equally as an interpretation of 
"substantial probability." 
No. 
97-1337 
 
11
¶23 Curiel presents the first issue on review as one 
involving interpretation of the term "substantially probable," 
although throughout his brief he refers to that phrasing of the 
term and "substantial probability" indiscriminately.  The State 
notes that the legislature used both phrasings in ch. 980, and 
suggests that the difference between them is at most a slight 
one and should not be given any significance; it proceeds to use 
the phrasings of the term interchangeably throughout its 
argument.  We also note that both the circuit court and the 
court of appeals used the terms interchangeably.  Neither party 
suggests that the phrasings require different definitions, and 
we are convinced that the legislature intended that the 
phrasings share a common meaning. 
¶24 To commit a person as sexually violent, the State must 
prove beyond a reasonable doubt, among other elements, that 
"[t]he person is dangerous to others because the person's mental 
disorder creates a substantial probability that he or she will 
engage in acts of sexual violence."  Wis. Stat. §§ 980.05(3)(a) 
and 980.02(2)(c).  The parties dispute the degree of likelihood 
required to satisfy the term “substantially probable.” 
¶25 Curiel argues that "substantially probable" means 
"extreme likelihood" and that, therefore, he could not be 
committed under ch. 980 unless the State proved beyond a 
reasonable doubt that he was dangerous to others because his 
mental disorder created an "extreme likelihood" that he would 
No. 
97-1337 
 
12
engage in future acts of sexual violence.5  The State disagrees, 
arguing 
that 
"substantially 
probable" 
means 
"substantially 
probable" and that ordinary persons can understand and apply 
this common sense term without further elucidation; it urges 
that we not redefine the term. 
¶26 The degree of likelihood intended by the use of the 
term "substantially probable" requires statutory interpretation. 
 The interpretation of a statute is a question of law that we 
review de novo.  State v. Setagord, 211 Wis. 2d 397, 406, 565 
N.W.2d 506 (1997).  The purpose of statutory interpretation is 
to discern the intent of the legislature.  Id.  In discerning 
the intent of the legislature, we first consider the language of 
the statute.  If the language of the statute clearly and 
unambiguously sets forth the legislative intent, we do not look 
beyond the statutory language to ascertain its meaning.  Id. 
¶27 In construing a statute, the general rule is that all 
words and phrases should be construed according to common and 
approved usage unless a different definition has been designated 
by the statutes.  Wis. Stat. § 990.01(1);  State v. Sher, 149 
Wis. 2d 1, 9, 437 N.W.2d 878 (1989).  We may resort to a 
dictionary to ascertain the common and approved usage of a term 
not defined by the statute.  State v. Chrysler Outboard Corp., 
                     
5 Curiel’s position on this point is difficult to pin down. 
 He at times argues that the term means “extreme likelihood.”  
At other times, he implicitly suggests that the term means “much 
more 
likely 
than 
not.” 
 
Indeed, 
his 
only 
suggested 
interpretation of the term in the court of appeals was “much 
more likely than not.”  
No. 
97-1337 
 
13
219 Wis. 2d 130, 168, 580 N.W.2d 203 (1998); see also HM 
Distrib. of Milwaukee v. Dept. of Agri., 55 Wis. 2d 261, 269, 
198 N.W.2d 598 (1972).  Our resort to a dictionary to determine 
the common and approved usage of the term does not render the 
term ambiguous.  State v. Sample, 215 Wis. 2d 487, 499, 573 
N.W.2d 187 (1998). 
¶28 Because "substantially probable" is not defined by 
statute, we turn to a dictionary.  We look first to the term 
"probable" and conclude that its most common and appropriate 
usage is "more likely than not."  The American Heritage 
Dictionary defines "probable" as an adjective meaning: "1. 
Likely to happen or to be true: War seemed probable in 1938.  
The home team, far ahead, is the probable winner.  2. Likely but 
uncertain; plausible." The American Heritage Dictionary of the 
English Language at 1443 (3d ed. 1992).  The common sense of 
"probable" in both of these definitions is that there is a 
greater likelihood that an event will happen than that it will 
not happen: that is, that it is more likely than not that the 
event will happen.  Further, in keeping with our conclusion that 
"probable" and "probability" are intended to share a common 
meaning, we note that the definitions of "probable" and 
"probability" are most closely analogous where "probable" is 
defined as "[h]aving more evidence for than against" and 
"probability" is defined as "a condition or state created when 
there is more evidence in favor of the existence of a given 
proposition than there is against it."  Black's Law Dictionary 
at 1201 (6th ed. 1990). 
No. 
97-1337 
 
14
¶29 The term "substantially" must also be given effect, 
otherwise the term is superfluous, a result we avoid in 
construing a statute.  Sher, 149 Wis. 2d at 9.  Although 
numerous definitions for "substantially" are provided by The 
American Heritage Dictionary, we conclude that the most common 
and appropriate definition of the term as used in ch. 980 is 
"[c]onsiderable in importance, value, degree, amount, or extent: 
won by a substantial margin."  The American Heritage Dictionary 
of the English Language at 1791.  A word which commonly denotes 
this sense of "substantially" is the term "much," defined as 
"[g]reat in quantity, degree, or extent."  Id. at 1183. 
¶30 Given the common and appropriate usage of the term, we 
interpret "substantially probable" as meaning "much more likely 
than not," and as so construed, find that the sections in which 
this term is found to be unambiguous.  The legislature intended 
that the State prove beyond a reasonable doubt that the person 
subject to the commitment proceedings is dangerous because his 
or her mental disorder makes it “much more likely than not” that 
the person will engage in future acts of sexual violence. 
¶31 We find unpersuasive both of Curiel's arguments in 
support 
of 
defining 
"substantially 
probable" 
as 
"extreme 
likelihood."  His first argument implicitly begins with the 
premise that the statute is not ambiguous, and as did we, he 
turns to a dictionary to identify the common and appropriate 
usage of the term.   Curiel agrees with our conclusion that 
probable 
means 
"more 
likely 
than 
not" 
but 
prefers 
that 
No. 
97-1337 
 
15
"substantially" be defined as "extreme."6  We disagree.  First, 
he provides us with no evidence that "extreme" is a common and 
appropriate 
usage 
of 
the 
term 
"substantially." 
 
Second, 
"substantially" and "extreme" are not synonyms"extreme" appears 
to us to involve a degree of certainty far greater than that 
suggested by the term "substantially".  Indeed, The American 
Heritage Dictionary defines "extreme" as an adjective meaning:  
"1. Most remote in any direction; outermost or farthest."  "2. 
Being in or attaining the greatest or highest degree; very 
intense."  "3. Extending far beyond the norm."  "4. Of the 
greatest severity."  The American Heritage Dictionary of the 
English Language, at 650.  None of these definitions suggests 
that "extreme" is a common and appropriate usage of the term 
"substantially." 
¶32 In a second argument, now with a view to the statute's 
ambiguity, Curiel offers legislative history as support for his 
view that "substantially probable" means "extreme likelihood."  
We 
have 
already 
determined 
that 
the 
term 
"substantially 
probable" is not ambiguous; in most circumstances we would not 
then consider matters outside the language of the statute for 
evidence of legislative intent.  However, because Curiel's equal 
protection argument is grounded in his interpretation of the 
legislative history of both ch. 980 and ch. 51, the Mental 
                     
6 Although when arguing that the evidence was not sufficient 
to support his verdict, he explicitly states that “much more 
likely than not” is an appropriate legal standard for the term 
“substantially probable.” 
No. 
97-1337 
 
16
Health 
Act, 
we 
believe 
that 
his 
argument 
detailing 
the 
legislative history of the two chapters should be addressed 
here. 
¶33 We understand Curiel's argument to be the following: 
The term "substantially probable" was adopted in ch. 980 to 
provide 
consistency 
with 
ch. 
51, 
which 
uses 
the 
term 
"substantial probability.”  Much in the manner in which the term 
is used in ch. 980, "substantial probability" is used in ch. 51 
to describe the degree to which a person is likely to harm 
himself, herself, or others before he or she could be found 
"dangerous."7  In 1972, the predecessor to the current ch. 51 was 
                     
7  Wis. Stat. § 51.20(1)2.a-d (1997-98), provides in part: 
2. The individual is dangerous because he or she 
does any of the following: 
a. 
Evidences 
a 
substantial 
probability 
of 
physical harm to himself or herself as manifested by 
evidence of recent threats of or attempts at suicide 
or serious bodily harm.  
b. 
Evidences 
a 
substantial 
probability 
of 
physical harm to other individuals as manifested by 
evidence 
of 
recent 
homicidal 
or 
other 
violent 
behavior, or by evidence that others are placed in 
reasonable 
fear of 
violent behavior and 
serious 
physical harm to them, as evidenced by a recent overt 
act, attempt or threat to do serious physical harm. . 
. . 
c. Evidences such impaired judgment, manifested 
by evidence of a pattern of recent acts or omissions, 
that there is a substantial probability of physical 
impairment or injury to himself or herself. . . . 
d. Evidences behavior manifested by recent acts 
or omissions that, due to mental illness, he or she is 
unable to satisfy basic needs for nourishment, medical 
care, shelter or safety without prompt and adequate 
treatment so that a substantial probability exists 
that death, serious physical injury, serious physical 
debilitation 
or 
serious 
physical 
disease 
will 
No. 
97-1337 
 
17
held unconstitutional in a number of respects, including the 
statute's 
lack 
of 
a 
requirement 
that 
the 
State 
prove 
dangerousness.  See Lessard v. Schmidt, 349 F. Supp. 1078, 1093 
(E.D. Wis. 1972), vacated and remanded, Schmidt v. Lessard, 414 
U.S. 473 (1974), order on remand, 379 F. Supp. 1376 (E.D. Wis. 
1974), vacated and remanded on other grounds, 421 U.S. 957 
(1975), order reinstated on remand, 413 F. Supp. 1318 (E.D. Wis. 
1976).  In discussing the degree of dangerousness that it 
believed was constitutionally required before a person could be 
involuntarily deprived of liberty, the court in Lessard used the 
term "extreme likelihood."  Referring to Humphrey v. Cady, 405 
U.S. 504, 509 (1972), the court wrote: 
 
[I]ts approval of a requirement that the potential for 
doing harm be 'great enough to justify such a massive 
curtailment of liberty' implies a balancing test in 
which the state must bear the burden of proving that 
there is an extreme likelihood that if the person is 
not confined he will do immediate harm to himself or 
others. 
Lessard, 349 F. Supp. at 1093.  Curiel concludes that because 
the legislature revised ch. 51 in response to Lessard, the term 
"substantial probability," used to define the likelihood that 
the person may do immediate harm, must have been intended to 
mean "extreme likelihood." 
¶34 We have reviewed the legislative history of both ch. 
980 and ch. 51 and are not convinced.  Moving as Curiel asks us 
to from the revision of ch. 51 in 1976 to the current ch. 980 
                                                                  
imminently ensue unless the individual receives prompt 
and adequate treatment for this mental illness. 
No. 
97-1337 
 
18
requires us to take too many leaps of faith to arrive at the 
conclusion he would have us reach. 
¶35 Our review of a Drafters Note from the Legislative 
Reference Bureau does satisfy us that the term "substantially 
probable" was chosen in an effort to use terms consistently 
throughout the statutes.  The author of the note explained that 
where the draft of ch. 980 had provided that "a person must be 
'likely' to commit predatory acts of sexual violence," he had 
"changed the language to say the person must be 'substantially 
probable' to commit such acts," and in doing so compared the new 
language to that found in Wis. Stat. §§ 51.20 (1)(a)2.a-d.  See 
LRB Drafter's Note to 1994 A.B. 3, (LRB-2975/P2dn) (Oct. 15, 
1993). 
¶36 While the language in ch. 980 may have been chosen to 
be consistent with language in ch. 51, we disagree with Curiel's 
proposition that "substantial probability" in ch. 51 means 
"extreme likelihood."  While it is true that the court in 
Lessard 
found 
the 
predecessor 
to 
the 
current 
ch. 
51 
unconstitutional in various respects, including the absence of 
proof of a person's dangerousness, there is no explicit evidence 
in 
the 
legislative 
history 
that 
the 
term 
"substantial 
probability" was chosen by the legislature as a term synonymous 
with "extreme likelihood."   
¶37 First, we note that the legislature did not originally 
choose the term "substantial probability” in ch. 51, it chose 
No. 
97-1337 
 
19
the term "substantial risk."  See Wis. Stat. § 51.20(1)(a)2.8  
Legislative history does not reveal that "substantial risk" was 
chosen to meet the language of Lessard.  And just as there is no 
evidence that “substantial risk” was chosen as a synonym of 
“extreme likelihood,” there is no evidence that when the 
legislature amended Wis. Stat. § 51.20 in 1977 and replaced 
“risk” with “probability,” 
it did 
so 
with 
a 
view 
that 
"probability" and "risk" were synonymous, or the view that 
"substantial 
probability" 
and 
"extreme 
likelihood" 
were 
synonymous.  See § 29, ch. 428, Laws of 1977 and Legislative 
Reference Bureau Analysis of 1977, Assembly Bill 898. 
¶38 We also find persuasive the State’s argument that 
legislative intent may be observed in the legislature's decision 
not to use the term "extreme likelihood."  The State suggests 
that the fact that the legislature chose a term other than that 
used in Lessard is evidence that the legislature did not intend 
an "extreme likelihood" standard.  The State further points out 
that when the legislature was revising ch. 51, Lessard was twice 
                     
8 Wis. Stat. 51.20(1)(a)2 (1975-76) provided that a 
person is dangerous because of: 
 
a. A substantial risk of physical harm to the subject 
individual as manifested by evidence of recent threats 
of or attempts at suicide or serious bodily harm; or 
 
b. A substantial risk of physical harm to other 
persons as manifested by evidence of recent homicidal 
or other violent behavior, or by evidence that others 
are placed in reasonable fear of violent behavior and 
serious physical harm to them, as evidenced by a 
recent overt act, attempt or threat to do such 
physical harm;  
No. 
97-1337 
 
20
appealed, remanded, and vacated, undermining the persuasive 
authority of the first decision.  In fact, we note that on 
remand in Lessard v. Schmidt, 379 F. Supp. 1376 (E.D. 1974), the 
court did not again use the term "extreme likelihood."  In 
describing the findings and standard of proof necessary for an 
order of commitment, the court wrote that they were "'mental 
illness and imminent dangerousness to self or others beyond a 
reasonable doubt' based at minimum upon a recent act, attempt or 
threat to do substantial harm."  Id. at 1381.  The absence of 
the "extreme likelihood" standard in this opinion does place a 
cloud upon the precedential worth of the court's earlier 
decision. 
¶39 As an additional document in support of his position, 
Curiel refers us to 71 Op. Att'y Gen. 34 (1982).  We agree with 
the court of appeals in its discussion of this opinion in State 
v. Kienitz, 221 Wis. 2d 275, 585 N.W.2d 609 (Ct. App. 1998), 
petition for review granted, 221 Wis. 2d 653, 588 N.W.2d 631 
(1998), that the opinion does not focus upon the meaning of 
"substantial probability" and therefore its worth is fairly 
suspect as evidence of legislative intent.  See id. at 299.  
Furthermore, we do not find that an attorney general opinion 
filed in 1982 is evidence of the legislature's intent when 
drafting a statute in 1976.  Cf. Juneau County v. Courthouse 
Employees, 221 Wis. 2d 630, 648, 585 N.W.2d 587 (1998) (post-
enactment interpretations by a legislative agency that worked 
with the legislature during the adoption of the statutory 
provisions may be an aid in determining legislative intent, 
No. 
97-1337 
 
21
although they may be less persuasive than reports issued prior 
to enactment). 
¶40 As do we, the State believes that the statute is not 
ambiguous, and that in the event that legislative history is 
considered, Curiel's position is without support.  However, it 
argues that we should not redefine the term "substantially 
probable" but leave the definition to the trier of fact.  We are 
not persuaded by the State's arguments.   
¶41 First, 
the 
State 
argues 
that 
since 
the 
term 
"substantial probability" has not been the source of any 
confusion in the application of ch. 51 and therefore has not 
required definition, by analogy the term should not need 
definition here.  This argument fails because unlike the use of 
the term in ch. 51, its use in ch. 980 has created difficulties: 
 in this case, the three experts offered three different 
personal working definitions; the court of appeals in this case, 
and the court of appeals in Kienitz, contributed two additional 
definitions. 
¶42 The State also suggests that just as this court has 
not defined other legal terms, the definitions of which are 
difficult to articulate, we should avoid doing so here.  It 
offers "reasonable doubt" and "substantial risk" as terms which 
although difficult to articulate have not been redefined in 
favor of allowing the trier of fact to employ his or her own 
understanding of the terms.  That we have chosen not to define 
the terms the State points to in the contexts in which they are 
used does not dissuade us from defining "substantially probable" 
No. 
97-1337 
 
22
here.  We believe that it is incumbent upon this court to define 
“substantially probable” in accord with legislative intent. 
¶43 In sum, we do not find that matters outside the 
language 
of 
the 
statute 
provide 
any 
evidence 
of 
the 
legislature’s intent in its use of the term “substantial 
probability.”  We do believe that the term is unambiguous, its 
common and appropriate usage meaning “much more likely than 
not.” 
Equal Protection 
¶44 As we have not defined the term "substantially 
probable" in ch. 980 as "extreme likelihood," Curiel challenges 
the constitutionality of ch. 980 on grounds of equal protection. 
 He claims a single substantive difference between the statutory 
schemes for commitment under ch. 51 and ch. 980: satisfying the 
standard of dangerousness requires the State prove to a greater 
likelihood the probability that a person will harm himself, 
herself, or another under ch. 51 than is required to prove that 
a person will sexually reoffend under ch. 980.  
¶45 Persons committed under chapters 51 and 980 are 
similarly situated for purposes of equal protection comparison. 
 State v. Post, 197 Wis. 2d 279, 318-19, 541 N.W.2d 115 (1995). 
 Equal protection guarantees require that persons similarly 
situated be accorded similar treatment  State v. Avila, 192 Wis. 
2d 870, 879, 532 N.W.2d 423 (1990)(citing Walters v. City of St. 
Louis, 347 U.S. 231, 237 (1954)).  However, this does not 
require that all persons be dealt with identically.  Id.  Equal 
protection is not violated where there exist reasonable and 
No. 
97-1337 
 
23
practical grounds for the classifications created by the 
legislature.  State v. Hezzie R., 219 Wis. 2d 849, 894, 580 
N.W.2d 660 (1998).  Nor is equal protection violated where 
similarly situated people are not treated differently. 
¶46 "When a party attacks a statute on the grounds that it 
denies 
equal 
protection 
under 
the 
law, 
the 
party 
must 
demonstrate that the state unconstitutionally treats members of 
similarly situated classes differently."  Post, 197 Wis. 2d at 
318.  Curiel's equal protection challenge fails because Curiel 
has not demonstrated that persons committed under ch. 51 are 
treated differently than persons committed under ch. 980. 
¶47 We have already considered the legislative histories 
of  ch. 980 and ch. 51 and have concluded that the histories do 
not support Curiel’s claim that ch. 51 requires that the State 
prove that the likelihood that a person will harm another is 
"extreme."  Both ch. 980 and ch. 51 employ a "substantial 
probability" standard.  We held that the term "substantially 
probable" as used in ch. 980 means "much more likely than not." 
 As the terms are to be used in a consistent manner between the 
chapters, we can conceive of no reason why the term as used in 
ch. 51 should be construed any differently than it is under ch. 
980. 
Void for Vagueness 
¶48 Curiel also argues that the court of appeals' failure 
to define "substantially probable" is a violation of his right 
to due processwe recognize his argument as one challenging the 
statute on grounds that it is void for vagueness.  Because we 
No. 
97-1337 
 
24
have concluded that "substantially probable" means "much more 
likely than not," Curiel's void for vagueness argument fails as 
well. 
¶49 The "principles underlying the void for vagueness 
doctrine . . . stem from concepts of procedural due process." 
State v. Popanz, 112 Wis. 2d 166, 172, 332 N.W.2d 750 (1983).  
"Due process requires that the law set forth fair notice of the 
conduct 
prohibited 
or 
required 
and 
proper 
standards 
for 
enforcement of the law and adjudication." Id.  Based upon these 
concepts of due process, a statute is void for vagueness if it 
fails to give notice to those wishing to obey the law that their 
conduct falls within the proscribed area, or if it fails to 
provide those who must enforce and apply the law objective 
standards with which to do so.  Id. at 172-73. 
¶50 Curiel challenges the statute because he believes that 
it fails to provide those who must apply the law objective 
standards with which to do so.  With this view of the void for 
vagueness doctrine in mind, we must determine whether the 
statute fails to be sufficiently definite to allow judges, 
juries and expert witnesses to apply the terms of ch. 980 
objectively to the question before them in order to determine 
whether to commit the defendant without having to create or 
apply their own standards.  See Popanz, 112 Wis. 2d at 173 
(citing State v. Courtney, 74 Wis. 2d 705, 711, 247 N.W.2d 714 
(1976)). 
¶51 As "substantially probable" means "much more likely 
than not," we have no doubt that this definition provides proper 
No. 
97-1337 
 
25
standards of adjudication.  The statute as defined is not so 
obscure that men of common intelligence must necessarily guess 
at its meaning and differ as to its applicability.  See Peissig 
v. Wisconsin Gas Co., 155 Wis. 2d 686, 699, 456 N.W.2d 348 
(1990). 
Sufficiency of the Evidence 
¶52 The parties dispute the appropriate standard by which 
we should review whether the evidence is sufficient to sustain 
the  verdict.  Curiel argues that because ch. 980 is a civil 
commitment proceeding, the standard of review should be a mixed 
question of law and fact.  Curiel relies on the standard of 
review articulated by the court of appeals in K.N.K. v. Buhler, 
139 Wis. 2d 190, 407 N.W.2d 281 (Ct. App. 1987), a case 
involving the protective placement of an incompetent person 
under ch. 55: 
 
We view the elements of protective placement set 
out in sec. 55.06(2), Stats., as questions of fact.  
See sec. 55.06(7) (trier of fact 'must find by clear 
and 
convincing 
evidence' 
the 
elements 
of 
sec. 
55.06(2)); 
sec. 
880.33, 
Stats. 
(referring 
to 
'findings' of incompetency). We will not overturn the 
circuit court's findings 
of 
fact 
unless 
clearly 
erroneous.  Sec. 805.17(2), Stats. However, we view 
the 
higher question 
regarding the 
necessity for 
protective placement as one of law because it involves 
the application of the facts as found by the court to 
a statutory concept.  See Nottelson v. DIHLR, 94 
Wis.2d 106, 115-16, 287 N.W.2d 763, 768 (1980).  We 
review questions of law independently from a circuit 
court's conclusions.  Ball v. District No. 4, Area 
Bd., 117 Wis. 2d 529, 537, 345 N.W.2d 389, 394 (1984). 
Id. at 198.  The State disagrees and argues that the standard of 
review should be that which applies to all sufficiency of the 
No. 
97-1337 
 
26
evidence challenges in criminal cases.  In State v. Poellinger, 
153 Wis. 2d 493, 451 N.W.2d 752 (1990), we explained the 
standard for reviewing the sufficiency of the evidence in a 
criminal case: 
 
an appellate court may not reverse a conviction unless 
the evidence, viewed most favorably to the state and 
the conviction, is so insufficient in probative value 
and force that it can be said as a matter of law that 
no trier of fact, acting reasonably, could have found 
guilt beyond a reasonable doubt. 
Id. at 501.   
¶53 Aside from describing these competing standards of 
review, neither party provides reasons why one or the other 
standard of review is appropriate for ch. 980 proceedings.  
Nonetheless, we conclude that the standard of review appropriate 
to commitment under ch. 980 is that standard we use to review 
criminal convictions. 
¶54 Most important to our decision is the fact that while 
ch. 980 is a civil proceeding, State v. Carpenter, 197 Wis. 2d 
252, 258, 541 N.W.2d 105 (1995), it shares many of the same 
procedural and constitutional features present in criminal 
prosecutions.  Pursuant to Wis. Stat. § 980.05(1m), "all rules 
of evidence in criminal actions apply" and "[a]ll constitutional 
rights available to a defendant in a criminal proceeding are 
available to the person" subject to the petition for commitment. 
 Furthermore, as in a criminal proceeding, the State's burden of 
proof under ch. 980 is beyond a reasonable doubt.  Wis. Stat. 
§ 980.05(3)(a). 
No. 
97-1337 
 
27
¶55 Because of the parallels between ch. 980 proceedings 
and criminal actions, review of ch. 980 proceedings will quite 
frequently involve applying much of the existing case law 
involving evidentiary and constitutional issues in criminal 
cases to ch. 980 appeals.  This may be particularly true where 
sufficiency of the evidence questions are interwoven with the 
discussions of the reasonable doubt standard.  For the purposes 
of clarity, particularly, use of the criminal standard of review 
is appropriate in ch. 980 appeals. 
¶56 Further, the only support offered by Curiel that the 
standard of review should be civil in nature is the language 
quoted above from K.N.K..  The court in K.N.K. explained that it 
would treat the statutory elements of ch. 55, governing 
protective placements, as findings of fact, reviewing them under 
the clearly erroneous standard.  K.N.K., 139 Wis. 2d at 198.  It 
explained further that it would review de novo "the higher 
question regarding the necessity for protective placement."  Id. 
 However, as a practical matter, the court found that the 
No. 
97-1337 
 
28
evidence was sufficient to support each element of the statute 
and reviewed nothing de novo.  See id. at 198-204.9 
¶57 We apply the standard of review applicable to criminal 
trials held to the court: 
 
The burden of proof upon the state is the same whether 
the case is tried before a jury or before a court.  
That burden is to prove the defendant guilty beyond a 
reasonable doubt.  The test applied upon appeal to 
this court is whether the 'evidence adduced, believed 
and rationally considered by the jury was sufficient 
to prove the defendant’s guilt beyond a reasonable 
doubt.' 
 
As the burden of proof is the same whether the trial 
is to the court or to a jury, the test to be applied 
to determine the sufficiency of the evidence is the 
same. 
 
When testing the sufficiency of the evidence, this 
court is not required to be convinced of the guilt of 
the defendant beyond a reasonable doubt, but only that 
the jury or the court could find the defendant guilty 
beyond a reasonable doubt. 
Gauthier v. State, 28 Wis. 2d 412, 415-16, 137 N.W.2d 101 
(1965)(internal citations omitted).  Of course, in the context 
in which this standard is applied, we recognize that the State's 
                     
9  The purpose evidently underlying Curiel's argument is 
that he would have us review de novo whether the evidence was 
sufficient to support a finding that it was substantially 
probable that he would engage in an act of sexual violence.  
However, the court in K.N.K. v. Buhler, 139 Wis. 2d 190, 407 
N.W.2d 281 (Ct. App. 1987), clearly treated the analogous 
"elemental" question under ch. 55 as one of fact and reviewed it 
under the clearly erroneous standard.  See id. at 202-03.  Even 
should we have decided to review ch. 980 actions as a mixed 
question of fact and law, the question of whether evidence 
established that it was substantially probable is one of fact 
and would be reviewed under a clearly erroneous standard, not de 
novo. 
No. 
97-1337 
 
29
burden is not to prove a person's guilt, but rather that the 
person subject to commitment is a sexually violent person. 
¶58 With respect to the only question on which Curiel 
claims the evidence was insufficient, the State has the burden 
of proving beyond a reasonable doubt that the person is 
dangerous to others because the person's mental disorder creates 
a substantial probability that he or she will engage in future 
acts of sexual violence.  Under the interpretation of the 
standard that we articulated above, the State must prove that 
because of the person's mental disorder, it is much more likely 
than not that the person will engage in future acts of sexual 
violence. 
¶59 Curiel believes that the evidence was insufficient 
because Sindberg, the only witness who testified that it was 
much more likely than not that he would reoffend sexually, is a 
less credible witness than either Waddell or Lodl.  Sindberg is 
less 
credible, 
argues 
Curiel, 
because 
Sindberg 
did 
not 
personally meet with him prior to reaching an opinion as to the 
likelihood that he would reoffend.  Curiel also argues that 
regardless of Sindberg's testimony, the fact that he and Waddell 
presented inconsistent testimony on the likelihood of him 
engaging in future acts of sexual violence is demonstrative that 
the State has not carried its burden. 
¶60 We find that the evidence was sufficient to establish 
beyond a reasonable doubt that it was "much more likely than 
not" that Curiel would engage in future acts of sexual violence. 
 To be sure, only Sindberg testified that he believed that it 
No. 
97-1337 
 
30
was "much more likely than not" that Curiel would reoffend 
sexually.  However, his testimony alone is sufficient to sustain 
the circuit court's judgment and order of commitment.  We 
explained in Gauthier that 
 
The credibility of the witnesses is properly the 
function of the jury or the trier of fact. . . .  It 
is only when the evidence that the trier of fact has 
relied upon is inherently or patently incredible that 
the appellate court will substitute its judgment for 
that of the fact finder, who has the great advantage 
of being present at the trial. 
Gauthier, 28 Wis. 2d at 416.  We have further explained that 
inherently or patently incredible evidence is that type of 
evidence which conflicts with nature or fully established or 
conceded facts.  Day v. State, 92 Wis. 2d 392, 400, 284 N.W.2d 
666 (1979). 
¶61 The circuit court clearly found Sindberg’s testimony 
credible.  At the close of the State’s case, the circuit court 
explained that there was nothing in the record to challenge 
Sindberg's opinion to the degree necessary to throw it out.  
Further, Curiel has not shown that Sindberg's evaluation, made 
No. 
97-1337 
 
31
without personally interviewing him, was incredible as to be 
undeserving of any weight.10 
¶62 Nor does the inconsistent testimony of Sindberg and 
Curiel render Sindberg’s testimony incredible as a matter of 
law.  Embry v. State, 46 Wis. 2d 151, 156-57, 174 N.W.2d 521 
(1970).  Even under the reasonable doubt burden of proof, the 
trier of fact is allowed to accept or reject inconsistent 
testimony.  Id.  In finding that Curiel was dangerous, the 
circuit court quite obviously resolved any inconsistency in the 
testimony of the experts in favor of finding that Curiel was 
much more likely than not to sexually reoffend.  However, it is 
the trier of fact’s task, not this court’s, to sift and winnow 
the credibility of the witnesses.  State v. Toy, 125 Wis. 2d 
216, 222, 371 N.W.2d 386 (Ct. App. 1985).  Certainly, as the 
circuit court noted, Sindberg’s testimony was worthy of belief. 
 The credibility of an expert witness and the weight the trier 
of fact is going to give to his testimony, as contrasted to 
other witnesses, is always an issue that is properly before the 
                     
10  In fact, were we to agree with Curielwhich we 
don'tthat an expert must personally meet the person subject to 
commitment, 
commitment 
under 
ch. 
980 
could 
be 
virtually 
impossible.  By the logic of Curiel's argument, the circuit 
court would be required to find the witness who had spoken with 
the subject of commitment more credible than the witness who did 
not.  One problem with this view is that as here, the defense 
witness will have access to the subject and the State witness 
may not.  The result of this approach is clear, and not one with 
which we agree: A person subject to commitment could avoid 
commitment merely by refusing to speak with the State's witness. 
No. 
97-1337 
 
32
trier of fact.  Kemp v. State, 61 Wis. 2d 125, 136, 211 N.W.2d 
793 (1973). 
¶63 Here, 
the 
circuit 
court 
was 
entitled 
to 
find 
Sindberg’s opinion more credible than that of Waddell or Lodl.  
The State’s evidence was not so lacking in probative value that 
no trier of fact, acting reasonably, could have drawn the 
appropriate inferences from the evidence adduced to find beyond 
a reasonable doubt that Curiel is a sexually violent person 
under ch. 980. 
¶64 Curiel has also maintained that the circuit court made 
an error in its finding of fact that Lodl testified that Curiel 
was a high risk for reoffending criminally.  We observe that 
immediately following this comment, the circuit court correctly 
recited the expert opinions of all three witnesses.  There is no 
evidence in the record that the circuit court relied upon its 
first misstatement in finding that Curiel was a sexually violent 
person.  
III 
¶65 In conclusion, this court holds that the standard by 
which to determine whether it is substantially probable that a 
person will engage in future acts of sexual violence is whether 
the likelihood is “much more likely than not.”  This standard 
does not violate the guarantees of equal protection, nor is it 
void for vagueness.  Finally, the evidence adduced at trial was 
sufficient to prove beyond a reasonable doubt that the defendant 
was much more likely than not to engage in future acts of sexual 
violence. 
No. 
97-1337 
 
33
By the Court.—The decision of the court of appeals is 
affirmed. 
 
¶66 JUSTICE DAVID T. PROSSER, JR. did not participate.   
 
 
 
 
1