Case Title: People v. Vang

Citation: 

Docket Number: s184212

State: california

Court: California Supreme Court

Date: 2011-10-31T00:00:00Z

Document:
1 
Filed 10/31/11 
 
 
 
IN THE SUPREME COURT OF CALIFORNIA 
 
 
 
THE PEOPLE, 
) 
 
 
) 
 
Plaintiff and Respondent, 
) 
 
 
) 
S184212 
 
v. 
) 
 
 
) 
Ct.App. 4/1 D054343 
XUE VANG, 
) 
 
) 
San Diego County 
 
Defendant and Appellant. 
) 
Super. Ct. No. SCD 213306 
 
____________________________________) 
 
An expert witness testified about whether a crime was gang related.  The 
Court of Appeal held that the trial court erred in permitting the expert to respond 
to hypothetical questions the prosecutor asked because the questions closely 
tracked the evidence in a manner that was only thinly disguised.  We disagree that 
the trial court erred.  It is required, not prohibited, that hypothetical questions be 
based on the evidence.  The questioner is not required to disguise the fact the 
questions are based on that evidence. 
I.  FACTS AND PROCEDURAL HISTORY 
These facts are taken largely from the Court of Appeal opinion. 
Defendants Xue Vang, Sunny Sitthideth, Danny Lê, and Dang Ha were 
convicted of assault by means of force likely to produce great bodily injury for 
assaulting 20-year-old William Phanakhon.  (Pen. Code, § 245, subd. (a)(1).)  The 
jury also found true an enhancement allegation that the defendants committed the 
assault “for the benefit of, at the direction of, or in association with any criminal 
 
2 
street gang, with the specific intent to promote, further, or assist in any criminal 
conduct by gang members . . . .”  (Pen. Code, § 186.22, subd. (b)(1); see generally 
People v. Albillar (2010) 51 Cal.4th 47, 59-68.)  The prosecution‟s theory was that 
the assault was committed for the benefit of the Tiny Oriental Crips (TOC), a 
criminal street gang. 
Phanakhon testified that he had associated for a while with members of the 
TOC, but denied being a gang member.  He met the four defendants in the fall and 
winter of 2007.  At trial, Sitthideth, Ha, and Lê, but not Vang, stipulated they were 
TOC members. 
During the evening of April 28, 2008, Phanakhon received a telephone call 
at his home.  The caller, whose voice seemed familiar, asked to “come over.”  
Phanakhon agreed.  He went to his garage and Vang arrived a short time later.  
Phanakhon also saw Lê peek inside the garage.  About five minutes after that, 
Vang asked Phanakhon if he wanted to go “hang out.”  Phanakhon followed Vang 
down the street.  He also saw Ha and Sitthideth walking towards the corner.  
When Phanakhon rounded the corner, someone struck him in the back of the head 
from behind.  He fell down and tried to protect his head from continued blows.  He 
then lost consciousness. 
San Diego Police Detective Dave Collins, who was conducting surveillance 
nearby, observed the assault.  He watched as four males approached the corner.  
Suddenly, three of the men began beating the fourth, but the victim did not fight 
back.  The victim fell to the ground, but two of the assailants pulled him up and hit 
him again.  Detective Collins observed two of the men back away while the third 
pulled out a stick or pipe and hit the victim on the head with it.  The victim fell to 
the ground a second time.  Detective Collins broadcast what he was seeing.  
Officer Michael Dewitt responded and arrived in time to see four men beating the 
victim. 
 
3 
The assailants fled.  The four defendants were arrested nearby.  The pipe or 
stick that Detective Collins observed was never found.  Paramedics transported 
Phanakhon to the hospital, where he was examined for head injuries, then 
released.  Phanakhon testified he did not know “for sure” why he was attacked, but 
he stated two possible reasons.  First, the defendants might have attacked him for 
disassociating himself from TOC.  Second, he might have been “checked” because 
he had heard something he was not supposed to hear. 
To show that the assault was gang related, the prosecution called an expert 
to testify about criminal street gangs.  The Court of Appeal opinion summarized 
his testimony:  “The prosecution called Detective Daniel Hatfield as its expert 
witness on criminal street gangs.  Detective Hatfield testified about the culture and 
habits of gangs, including member-on-member discipline for no longer hanging 
out with the gang or not „putting in work.‟  Turning to TOC, he described it as a 
predominately Laotian group that split off from a larger gang set in the early 
1990‟s and claimed Linda Vista as its territory.  Detective Hatfield identified three 
separate predicate offenses committed by its members and opined that TOC was a 
criminal street gang.  Given the stipulation, there was no dispute that Ha, 
Sitthideth and Lê were members of TOC.  Detective Hatfield believed that Vang 
and the victim Phanakhon were also gang members.” 
In part, Detective Hatfield responded to hypothetical questions.  As the 
Court of Appeal described it, “Over defense objection, Detective Hatfield 
responded to two hypothetical questions from the prosecution that tracked the 
facts of the case.”1  On direct examination, the prosecutor asked about a 
                                              
1  
It would be more accurate to say that the questions tracked the evidence, 
not the facts of the case.  The jury determines what the facts are, and it may or 
may not believe all of the evidence. 
 
4 
hypothetical assault on a “young baby gangster.”  After stating the hypothetical 
facts, the prosecutor asked:  “Based on the facts of that hypothetical, do you have 
an opinion as to whether this particular crime was committed for the benefit of and 
[in] association with or at the direction of the Tiny Oriental Crips street gang?”  
Detective Hatfield said he did have an opinion based on those facts.  He believed 
that “they did this to keep the gang strong because the gang set is only as strong as 
its weakest member.  And that member did something to the TOC gang for him to 
be victimized in this case.  They put him in check.  They brought him back in line 
over some perceived wrong that this individual did to that set, and the victim may 
not even know what he or she did in this incident.”  He stated that the assault 
would benefit TOC and was committed in association with TOC and at the 
direction of TOC members. 
On redirect examination, the prosecutor stated additional hypothetical facts 
based on the evidence, and asked whether, under those hypothetical facts, 
Detective Hatfield had “an opinion about whether or not this was a gang-
motivated attack.”  The witness said he did.  The prosecutor then asked, “What is 
your opinion about the gang motivation behind the attack that has been described 
in the hypothetical?”  Detective Hatfield responded, “The reason why I feel that it 
was gang motivated is what you told me exactly as far as the fact that this 
individual, in this hypothetical, is saying that he had been hanging.  He had been 
associating with the documented gang members.  He tells me that.  That tells me 
that . . . he has been a gang member, and especially in that hypothetically if he 
meets that criteria, that fact that — he doesn‟t have to know the reason why he is 
being attacked — doesn‟t have to know.  There could be a perception or a 
paranoia from the gang members that are attacking him that he did something to 
tick off the gang set.  The fact that he was lured out to where he was attacked tells 
me that that was planned.  The fact that it was done in concert with known 
 
5 
documented gang members, that they work together to do what they did to the 
victim, tells me that this is a gang-motivated incident.  It wasn‟t about friends 
fighting among one another.” 
The court sentenced Vang, Sitthideth, and Lê to state prison for six, four, 
and 12 years, respectively, and placed Ha on probation.  They appealed.  The 
Court of Appeal found that the trial court erred in permitting Detective Hatfield to 
respond to the hypothetical questions but found the error harmless.  It also rejected 
other arguments defendants made.  It modified one condition of probation as to Ha 
and otherwise affirmed the judgments. 
All four defendants petitioned for review.  We granted review and limited 
the issues to (1) whether the Court of Appeal correctly found that the trial court 
erred in permitting the use of the hypothetical questions, and (2) if so, whether the 
Court of Appeal correctly found the error harmless.  On our own motion, we 
severed Vang‟s case from that of the other defendants and deferred further briefing 
by the other defendants pending our decision in this case. 
II. DISCUSSION 
“California law permits a person with „special knowledge, skill, experience, 
training, or education‟ in a particular field to qualify as an expert witness (Evid. 
Code, § 720) and to give testimony in the form of an opinion (id., § 801).  Under 
Evidence Code section 801, expert opinion testimony is admissible only if the 
subject matter of the testimony is „sufficiently beyond common experience that the 
opinion of an expert would assist the trier of fact.‟  (Id., subd. (a).)  The subject 
matter of the culture and habits of criminal street gangs . . . meets this criterion.”  
(People v. Gardeley (1996) 14 Cal.4th 605, 617 (Gardeley).) 
The issue before us concerns the propriety of permitting the gang expert to 
respond to the hypothetical questions the prosecution asked regarding whether 
defendants‟ assault on Phanakhon was gang related.  Defendant argues the trial 
 
6 
court erred “when it permitted the prosecutor to ask a detailed hypothetical 
question, closely tracking the facts in this case, about whether the assault was 
gang-motivated.”  The Court of Appeal summarized the issue:  “Defendants argue 
that the trial court abused its discretion when it allowed Detective Hatfield to 
testify in response to a hypothetical question that the assault on Phanakhon, thinly 
disguised in the hypothetical as „young baby gangster,‟ was for the benefit of TOC 
and was gang motivated.” 
Relying on People v. Killebrew (2002) 103 Cal.App.4th 644 (Killebrew), 
the Court of Appeal found that the trial court erred.  It “agree[d] with the rule of 
Killebrew that an expert witness may not offer an opinion on what a particular 
defendant is thinking.  (Killebrew, supra, 103 Cal.App.4th at p. 647.)  And more 
importantly here, the prosecutor may not circumvent that rule by asking the expert 
a hypothetical question that thinly disguises the defendant‟s identity.”  It also said 
that “the trial court abused its discretion by admitting Detective Hatfield‟s 
testimony regarding defendants‟ knowledge and intent based on its apparent belief 
that such testimony was admissible so long as it was presented in the form of a 
hypothetical. . . .  [T]he prosecution may not use a hypothetical question to 
conceal an expert‟s improper testimony on the real defendants‟ subjective 
knowledge and intent.” 
The Court of Appeal interpreted Killebrew, supra, 103 Cal.App.4th 644, as 
prohibiting hypothetical questions if they too closely track the evidence, then 
concluded that “Detective Hatfield‟s testimony in response to the two hypothetical 
questions violated the rule in Killebrew.  The only apparent differences between 
the trial testimony and the hypothetical were the names of the parties.  In the 
hypothetical question, the prosecution called the victim „young baby gangster‟ 
instead of Phanakhon and called the four defendants „three baby gangsters and one 
O.G.,‟ that is, „original gangster.‟  Indeed, one of the defense attorneys reported 
 
7 
hearing „laughter or tittering from the jury‟ when Ha‟s defense attorney objected 
to the use of the hypothetical at an earlier stage in Detective Hatfield‟s testimony.” 
The Court of Appeal erred in condemning the hypothetical questions 
because they tracked the evidence in a manner that was only “thinly disguised.”  
“Generally, an expert may render opinion testimony on the basis of facts given „in 
a hypothetical question that asks the expert to assume their truth.‟  (1 McCormick 
on Evidence (4th ed. 1992) § 14, p. 58.)”  (Gardeley, supra, 14 Cal.4th at p. 618.)  
The hypothetical question we approved in Gardeley was similar to the ones here.  
“After giving Detective Boyd a „hypothetical‟ based on the facts of the assault in 
this case . . . by three Family Crips members, the prosecutor asked Boyd if in his 
expert opinion an attack as described would be „gang-related activity.‟  Boyd 
responded that it was a „classic‟ example of gang-related activity . . . .”  (Id. at p. 
619, italics added.)  We held that this testimony helped support the jury‟s finding 
that the crime of that case was gang related.  (Id. at pp. 619-620.)  The 
hypothetical questions in this case were just as proper as the one described in 
Gardeley.  (See also People v. Ward (2005) 36 Cal.4th 186, 209 [upholding “fact-
specific hypothetical questions to elicit testimony from [gang] experts that a gang 
member going into rival gang territory — like defendant — would do so as a 
challenge and would protect himself with a weapon”]; People v. Garcia (2007) 
153 Cal.App.4th 1499, 1505, 1513-1514 [prosecutor properly stated hypothetical 
facts, then asked the expert, “ „do you have an opinion as to whether this particular 
offense was committed for the benefit of, or in association with the criminal street 
gang?‟ ”].) 
Use of hypothetical questions is subject to an important requirement.  
“Such a hypothetical question must be rooted in facts shown by the evidence . . . .”  
(Gardeley, supra, 14 Cal.4th at p. 618; see also People v. Moore (2011) 51 Cal.4th 
386, 405; People v. Richardson (2008) 43 Cal.4th 959, 1008; People v. Ward, 
 
8 
supra, 36 Cal.4th at p. 209; People v. Boyette (2002) 29 Cal.4th 381, 449; People 
v. Gonzalez (2005) 126 Cal.App.4th 1539, 1551, fn. 4; 1 Jefferson, Cal. Evidence 
Benchbook (Cont. Ed. Bar 4th ed. 2010 update) § 30.48, p. 687.)  A hypothetical 
question need not encompass all of the evidence.  “It is true that „it is not 
necessary that the question include a statement of all the evidence in the case.  The 
statement may assume facts within the limits of the evidence, not unfairly 
assembled, upon which the opinion of the expert is required, and considerable 
latitude must be allowed in the choice of facts as to the basis upon which to frame 
a hypothetical question.‟  (People v. Wilson (1944) 25 Cal.2d 341, 349.)  On the 
other hand, the expert‟s opinion may not be based „on assumptions of fact without 
evidentiary support [citation], or on speculative or conjectural factors . . . .‟ ”  
(People v. Richardson, supra, at p. 1008; see also 3 Witkin, Cal. Evidence (4th ed. 
2000) Presentation at Trial, § 194, p. 258 [“The traditional method of taking the 
opinion evidence of an expert is the hypothetical question.  This may be framed on 
any theory that can be deduced from the evidence, and the questioner may assume 
any facts within the limits of the evidence and omit any facts not deemed 
material.”].)  But, however much latitude a party has to frame hypothetical 
questions, the questions must be rooted in the evidence of the case being tried, not 
some other case. 
The reason for this rule should be apparent.  A hypothetical question not 
based on the evidence is irrelevant and of no help to the jury.  “ „Exclusion of 
expert opinions that rest on guess, surmise or conjecture [citation] is an inherent 
corollary to the foundational predicate for admission of the expert testimony:  will 
the testimony assist the trier of fact to evaluate the issues it must decide?‟ ”  
(People v. Richardson, supra, 43 Cal.4th at p. 1008.)  Expert testimony not based 
on the evidence will not assist the trier of fact.  Thus, “[a]lthough the field of 
permissible hypothetical questions is broad, a party cannot use this method of 
 
9 
questioning a witness to place before the jury facts divorced from the actual 
evidence and for which no evidence is ever introduced.”  (People v. Boyette, 
supra, 29 Cal.4th at p. 449.) 
As applied here, this rule means that the prosecutor‟s hypothetical 
questions had to be based on what the evidence showed these defendants did, not 
what someone else might have done.  The questions were directed to helping the 
jury determine whether these defendants, not someone else, committed a crime for 
a gang purpose.  Disguising this fact would only have confused the jury.  
The parties agree that the hypothetical questions of this case were based on 
the evidence.  But the Court of Appeal found these questions were too closely 
based on the evidence in a manner that was only “thinly disguised.”  This 
conclusion transforms the requirement that a hypothetical question be rooted in 
the evidence into a prohibition — or at least into the confounding rule that the 
party posing the question must disguise from the jury the fact it is rooted in the 
evidence — and not “thinly,” it appears, but thickly. 
In support of this argument, defendant Vang and the Court of Appeal rely 
primarily on Killebrew, supra, 103 Cal.App.4th 644.  We discussed Killebrew in 
People v. Gonzalez (2006) 38 Cal.4th 932 (Gonzalez).  In Gonzalez, the defendant 
argued that testimony by the gang expert (Sergeant Garcia) violated Killebrew by 
expressing an opinion, in response to hypothetical questions, regarding whether 
some of the witnesses had been intimidated by gang members.  We rejected the 
argument.  “Sergeant Garcia merely answered hypothetical questions based on 
other evidence the prosecution presented, which is a proper way of presenting 
expert testimony.”  (Gonzalez, supra, at p. 946, citing Gardeley, supra, 14 Cal.4th 
at p. 618.)  We explained that the “witness did not express an opinion about 
whether the particular witnesses in this case had been intimidated.  [Citation.]  [¶]  
It is true that Sergeant Garcia‟s opinion, if found credible, might, together with 
 
10 
other evidence, lead the jury to find the witnesses were being intimidated . . . .  But 
this circumstance makes the testimony probative, not inadmissible.”  (Gonzalez, 
supra, at p. 947.)2 
We explained Killebrew‟s limited significance.  “People v. Killebrew, 
supra, 103 Cal.App.4th 644, is somewhat unclear in this regard.  Although its 
legal discussion states that the expert „informed the jury of his belief of the 
suspects‟ knowledge and intent on the night in question,‟ its factual account states 
that „[t]hrough the use of hypothetical questions, Darbee [the expert] testified that 
each of the individuals in the three cars‟ had certain knowledge and intent.  (Id. at 
p. 658.)  The opinion never specifically states whether or how the expert referred 
to specific persons, rather than hypothetical persons.  Obviously, there is a 
difference between testifying about specific persons and about hypothetical 
persons.  It would be incorrect to read Killebrew as barring the questioning of 
expert witnesses through the use of hypothetical questions regarding hypothetical 
persons.  As explained in People v. Gonzalez, supra, 126 Cal.App.4th at page 
1551, footnote 4, use of hypothetical questions is proper.”  (Gonzalez, supra, 38 
Cal.4th at p. 946, fn. 3, italics added.)3 
                                              
2 
Throughout our discussion, we cited with approval People v. Gonzalez, 
supra, 126 Cal.App.4th 1539 (a different Gonzalez), which stated the relevant law 
and discussed Killebrew correctly. 
3  
The Court of Appeal described this discussion as “dicta,” a word commonly 
used as shorthand for the term “obiter dictum.”  We do not believe the discussion 
was obiter dictum.  Black‟s Law Dictionary defines “obiter dictum” as “[a] 
judicial comment made while delivering a judicial opinion, but one that is 
unnecessary to the decision in the case and therefore not precedential (although it 
may be considered persuasive). — Often shortened to dictum or, less commonly, 
obiter.”  (Black‟s Law Dict. (9th ed. 2009) p. 1177, col. 2.)  (“Dicta” is, of course, 
the plural form of “dictum.”  (Ibid.)) 
 
The defendant in Gonzalez, supra, 38 Cal.4th 932, relied on Killebrew, 
supra, 103 Cal.App.4th 644, to argue the trial court had erred in permitting 
 
(footnote continued on next page) 
 
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To the extent that Killebrew, supra, 103 Cal.App.4th 644, was correct in 
prohibiting expert testimony regarding whether the specific defendants acted for a 
gang reason,4 the reason for this rule is not that such testimony might embrace the 
ultimate issue in the case.  “Testimony in the form of an opinion that is otherwise 
admissible is not objectionable because it embraces the ultimate issue to be 
decided by the trier of fact.”  (Evid. Code, § 805; see People v. Prince, supra, 40 
Cal.4th at p. 1227; People v. Olguin (1994) 31 Cal.App.4th 1355, 1370-1371.)  
Rather, the reason for the rule is similar to the reason expert testimony regarding 
the defendant‟s guilt in general is improper.  “A witness may not express an 
opinion on a defendant‟s guilt.  [Citations.]  The reason for this rule is not because 
guilt is the ultimate issue of fact for the jury, as opinion testimony often goes to 
the ultimate issue.  [Citations.]  „Rather, opinions on guilt or innocence are 
inadmissible because they are of no assistance to the trier of fact.  To put it another 
                                                                                                                                                              
 
(footnote continued from previous page) 
 
hypothetical questions.  We rejected the argument, partly on the basis that it is 
incorrect to read Killebrew as prohibiting the “questioning of expert witnesses 
through the use of hypothetical questions.”  (Gonzalez, supra, at p. 946, fn. 3.)  
The comment in Gonzalez in question thus directly responded to the defendant‟s 
argument and was necessary to fully explain why that argument lacked merit. 
 
In any event, we repeat what we said in Gonzalez:  We disapprove of any 
interpretation of Killebrew, supra, 103 Cal.App.4th 644, as barring, or even 
limiting, the use of hypothetical questions.  Even if expert testimony regarding the 
defendants themselves is improper, the use of hypothetical questions is proper. 
4  
It appears that in some circumstances, expert testimony regarding the 
specific defendants might be proper.  (See People v. Valdez (1997) 58 Cal.App.4th 
494, 507, cited with approval in People v. Prince (2007) 40 Cal.4th 1179, 1227.)  
The question is not before us.  Because the expert here did not testify directly 
about defendants, but only responded to hypothetical questions, we will assume 
for present purposes the expert could not properly have testified about defendants 
themselves. 
 
12 
way, the trier of fact is as competent as the witness to weigh the evidence and 
draw a conclusion on the issue of guilt.‟ ”  (People v. Coffman and Marlow (2004) 
34 Cal.4th 1, 77; see also People v. Prince, supra, at p. 1227.) 
Here, for example, Detective Hatfield had no personal knowledge whether 
any of the defendants assaulted Phanakhon and, if so, how or why; he was not at 
the scene.  The jury was as competent as the expert to weigh the evidence and 
determine what the facts were, including whether defendants committed the 
assault.  So he could not testify directly whether they committed the assault for 
gang purposes.  But he properly could, and did, express an opinion, based on 
hypothetical questions that tracked the evidence, whether the assault, if the jury 
found it in fact occurred, would have been for a gang purpose.  “Expert opinion 
that particular criminal conduct benefited a gang” is not only permissible but can 
be sufficient to support the Penal Code section 186.22, subdivision (b)(1), gang 
enhancement.  (People v. Albillar, supra, 51 Cal.4th at p. 63.)  It is true that 
Detective Hatfield‟s opinion, if found credible, might, together with the rest of the 
evidence, cause the jury to find the assault was gang related.  “But this 
circumstance makes the testimony probative, not inadmissible.”  (Gonzalez, supra, 
38 Cal.4th at p. 947.)  It is also true that, because defendants assaulted their victim 
under the watchful eye of a police officer conducting surveillance, the jury would 
likely credit the evidence that they did commit the assault.  But that is merely 
unfortunate for defendants, not a reason to exclude probative and permissible 
expert testimony. 
To the extent Killebrew, supra, 103 Cal.App.4th 644, purported to 
condemn the use of hypothetical questions, it overlooked the critical difference 
between an expert‟s expressing an opinion in response to a hypothetical question 
and the expert‟s expressing an opinion about the defendants themselves.  
Killebrew stated that the expert in that case “simply informed the jury of his belief 
 
13 
of the suspects‟ knowledge and intent on the night in question, issues properly 
reserved to the trier of fact.”  (Killebrew, supra, 103 Cal.App.4th at p. 658.)  But, 
to the extent the testimony responds to hypothetical questions, as in this case (and, 
it appears, in Killebrew itself), such testimony does no such thing.  Here, the 
expert gave the opinion that an assault committed in the manner described in the 
hypothetical question would be gang related.  The expert did not give an opinion 
on whether defendants did commit an assault in that way, and thus did not give an 
opinion on how the jury should decide the case. 
The trial court understood precisely the distinction between (1) not 
permitting the expert to opine that the particular defendants committed a crime for 
a gang purpose, and (2) permitting the expert to express his opinion in response to 
hypothetical questions.  The court sustained an objection to a question regarding 
whether a particular defendant had knowledge of the gang activities.  In sustaining 
the objection, it explained to the jury that “the law doesn‟t allow the expert to 
come in and say exactly what somebody else‟s mind — what was in their mind.  
All of the evidence is presented to you for you to make that decision.”  It only 
permitted the expert to give an opinion whether an assault would have had a gang 
purpose in response to hypothetical questions.  The court acted correctly in this 
regard. 
The Court of Appeal, and perhaps the author of the separate opinion in this 
court, may be concerned that permitting these hypothetical questions invades the 
province of the jury.5  However, as noted, expert testimony is permitted even if it 
                                              
5  
Justice Werdegar‟s separate opinion seems to make one or more of the 
following arguments:  (1) expert testimony is simply not admissible regarding 
whether a crime is gang related; (2) such testimony may not be given in the form 
of opinions based on hypothetical questions; (3) there was something improper 
 
(footnote continued on next page) 
 
14 
embraces the ultimate issue to be decided.  (Evid. Code, § 805.)  The jury still 
plays a critical role in two respects.  First, it must decide whether to credit the 
expert‟s opinion at all.  Second, it must determine whether the facts stated in the 
hypothetical questions are the actual facts, and the significance of any difference 
                                                                                                                                                              
 
(footnote continued from previous page) 
 
about the specific hypothetical questions of this case; or (4) there was something 
improper about the specific answers of this case. 
 
However:  (1)  It has long been settled that expert testimony regarding 
whether a crime was gang related is admissible.  (People v. Albillar, supra, 51 
Cal.4th at p. 63; People v. Gardeley, supra, 14 Cal.4th at p. 619.)  And for good 
reason.  Such matters are sufficiently beyond common experience that expert 
testimony would assist the jury.  (People v. Gonzalez, supra, 38 Cal.4th at p. 945.)  
For example, “It is difficult to imagine a clearer need for expert explication than 
that presented by a subculture in which this type of mindless retaliation promotes 
„respect.‟ ”  (People v. Olguin, supra, 31 Cal.App.4th at p. 1384; see People v. 
Gonzalez, supra, at pp. 945-946.)  (2)  It has also long been settled that expert 
testimony generally, and expert testimony regarding whether a crime is gang 
related specifically, may be given in response to hypothetical questions.  (E.g., 
People v. Gardeley, supra, at pp. 618, 619; People v. Garcia, supra, 153 
Cal.App.4th at pp. 1505, 1513-1514.)  We are aware of nothing so distinctive 
about expert gang testimony that it should be an exception to the general rule 
permitting the use of hypothetical questions.  (3)  The Court of Appeal criticized 
the hypothetical questions of this case solely because they only thinly disguised 
the fact they were based on the evidence, a criticism clearly unwarranted.  The 
separate opinion does not specify what else might have been wrong with the 
questions.  Neither the Evidence Code nor any other authority requires that 
hypothetical questions be formulated in any particular fashion.  The questions here 
were similar to questions found valid in cases such as People v. Gardeley, supra, 
at page 619, and People v. Garcia, supra, at pages 1513-1514.  (4)  The expert‟s 
answers here fully responded to the questions.  Although answers to hypothetical 
questions, as to any questions, must respond to those questions, neither the 
Evidence Code nor any other authority requires any particular answers to 
questions or the use or avoidance of any particular words.  The expert gave his 
opinion and explained it.  We see nothing improper in doing so. 
 
Whether to accept the expert‟s opinion and, if so, how to apply it to the 
actual case was for the jury to determine.  But the trial court properly permitted the 
questions and answers. 
 
15 
between the actual facts and the facts stated in the questions.  The trial court 
instructed the jury on both of these roles.  It told the jury that “the meaning and the 
importance of any [expert] opinion are for you to decide,” and that “you may 
disregard any opinion you find to be unbelievable, unreasonable, or unsupported 
by the evidence.”  It also instructed the jury specifically about hypothetical 
questions:  “In examining an expert witness, the expert witness may be asked a 
hypothetical question.  A hypothetical question asks a witness to assume that 
certain facts are true and then give an opinion based on those facts.  It’s up to you 
to decide whether an assumed fact has, in fact, been proved.  If you conclude that 
an assumed fact is not true, consider the effect of the expert‟s reliance on that fact 
in evaluating the expert‟s opinion.”  (Italics added; see CALCRIM No. 332; see 
also People v. Prince, supra, 40 Cal.4th at p. 1227 [citing with approval the 
comparable CALJIC instructions on expert testimony in upholding the expert 
testimony in that case]; People v. Boyette, supra, 29 Cal.4th at p. 452 [citing with 
approval the comparable CALJIC instruction on hypothetical questions in 
upholding the hypothetical questions in that case].) 
Often the evidence presented in a trial may support varying factual 
findings, and the differences in the possible factual findings might affect the 
expert‟s opinion.  The parties may, if they wish, explore with the expert various 
factual scenarios the evidence suggests and how they might affect the expert‟s 
opinion.  The prosecution may do so on direct examination (and, if otherwise 
appropriate, on redirect examination); the defendant may do so on cross- (or 
recross-) examination.  Such questioning might assist the jury.  Moreover, the 
defendant has the opportunity during argument to stress to the jury that an expert‟s 
testimony is one opinion concerning the motivations of actors in a hypothetical 
scenario; the expert has no personal knowledge concerning the particular 
defendant‟s state of mind.  The jury must still find the facts after considering all of 
 
16 
the evidence, the court‟s instructions, and the parties‟ arguments.  Hypothetical 
questions must not be prohibited solely because they track the evidence too 
closely, or because the questioner did not disguise the fact the questions were 
based on the evidence. 
Over the years, commentators have sometimes criticized the use of 
hypothetical questions, but not in a way that supports the conclusion that the 
questioner must disguise the fact they are based on the evidence, or that would 
support banning such questions entirely.  (E.g., The New Wigmore:  A Treatise on 
Evidence, Expert Evidence (2004) The Bases for Expert Testimony, § 3.4, pp. 93-
95; 1 McCormick on Evidence (6th ed. 2006) § 16, pp. 98-99; see generally 3 
Witkin, Cal. Evidence, supra, § 194, pp. 259-260.)  The criticisms generally are 
that hypothetical questions might be unduly partisan or posed in an argumentative 
or obfuscating manner, might be overlong, might misrepresent or omit important 
facts, might confuse the jury, and might improperly be used as a “closing 
argument midstream.”  (The New Wigmore, supra, § 3.4, p. 94.)  Wigmore‟s 
solution was to allow but not require use of hypothetical questions.  (Id. at p. 95.)  
McCormick suggested that one safeguard against abuse “is the cross-examiner‟s 
rights; on cross-examination the adversary may supply omitted facts and ask the 
expert if his opinion would be modified by them.  A further safeguard is the 
judge‟s authority; if she deems the question unfair, the trial judge may require that 
the hypothesis be reframed to supply an adequate basis.”  (1 McCormick on 
Evidence, supra, § 14, p. 90, fns. omitted.) 
Thus, there are dangers with hypothetical questions.  Over objection, the 
trial court should be vigilant to ensure that they are used fairly.  But it is not a 
legitimate objection that the questioner failed to disguise the fact the question was 
based on the evidence.  As applied to this case, it was not a legitimate objection 
 
17 
that the prosecutor failed to disguise the fact he was asking about an assault based 
on the one that the evidence showed defendants committed. 
Defendant Vang also cites cases involving statutes that prohibit an expert to 
testify on a certain point.  The cases generally hold that a party may not 
circumvent the prohibition by using hypothetical questions.  (People v. Bordelon 
(2008) 162 Cal.App.4th 1311, 1326-1328; U.S. v. Boyd (D.C. Cir. 1995) 55 F.3d 
667, 670-672; U.S. v. Thigpen (11th Cir. 1993) 4 F.3d 1573, 1579-1580; U.S. v. 
Dennison (10th Cir. 1991) 937 F.2d 559, 564-565; U.S. v. Manley (11th Cir. 1990) 
893 F.2d 1221, 1223-1225.)  The cases are inapposite.  If a statute prohibits an 
expert from expressing an opinion on a point, it may be correct not to allow the 
expert to express that opinion by using hypothetical questions.  But no statute 
prohibits an expert from expressing an opinion regarding whether a crime was 
gang related.  Indeed, is settled that an expert may express such an opinion.  To 
the extent the expert may not express an opinion regarding the actual defendants, 
that is because the jury can determine what the defendants did as well as an expert, 
not because of a prohibition against the expert opining on the entire subject.  
Using hypothetical questions is just as appropriate on this point as on other matters 
about which an expert may testify. 
Accordingly, we conclude the trial court did not err in permitting the 
hypothetical questions of this case.  This conclusion makes it unnecessary to 
determine whether the Court of Appeal correctly found the perceived error 
harmless. 
 
18 
 
III.  CONCLUSION 
Although the Court of Appeal erroneously found error, it also found the 
error harmless.  Accordingly, it reached the correct result.  For this reason, we 
affirm the judgment. 
 
CHIN, J. 
WE CONCUR: 
 
CANTIL-SAKAUYE, C.J. 
KENNARD, J. 
BAXTER, J. 
CORRIGAN, J. 
LIU, J. 
 
 
 
1 
 
 
 
 
 
 
 
 
CONCURRING OPINION BY WERDEGAR, J. 
 
 
Because I find no probability the jury would have returned a verdict more 
favorable to defendant had it heard the expert witness‟s explanation of gang 
culture and practices, as it did, but not his opinion that the crime was gang 
motivated, as it also did, I concur in the judgment.  But I do not join the majority 
opinion because I find it neither correctly states nor persuasively responds to the 
true question before us. 
The majority characterizes the Court of Appeal‟s holding to be that 
hypothetical questions must not too closely track the evidence.  But both the 
appellate court and defendant accept that to be of any value, a hypothetical 
question must be based on the evidence.  To say the Court of Appeal was 
transforming “the requirement that a hypothetical question be rooted in the 
evidence into a prohibition,” as the majority does (maj. opn., ante, at p. 9), is 
untrue and also evades the real issue in this case. 
The Court of Appeal concluded the expert‟s opinion was inadmissible not 
because it was based on assumed facts that only thinly disguised the prosecution‟s 
evidence, but because based on those facts the expert was allowed to express an 
opinion that effectively directed the jurors how to resolve the issue of defendant‟s 
motive:  “ „[T]his is a gang-motivated incident.  It wasn‟t about friends fighting 
among one another.‟ ”  Although “[t]he culture and habits of criminal street gangs 
are appropriate subjects for expert testimony . . . ,” the Court of Appeal observed, 
 
2 
“[e]xpert opinion on a specific defendant’s subjective knowledge and intent is 
not.”  (Italics added.) 
I can think of two theories for rejecting the Court of Appeal‟s conclusion.  
First, it might be reasoned the expert‟s opinion was admissible because, contrary 
to the Court of Appeal‟s belief, although based on a hypothetical tracking the 
prosecution‟s evidence, the expert‟s opinion did not direct the jury to conclude 
that the specific defendant‟s crime was gang motivated.  Alternatively, it might be 
reasoned that even after the expert had instructed the jurors generally on gang 
culture and practices, the jurors‟ inexperience in such matters rendered them 
incapable of determining motive in the circumstances without first hearing the 
expert‟s opinion on the issue.  The majority seems to adopt the first theory; in my 
view, the outcome of this case requires consideration of the second. 
The majority appears to accept that an expert may not directly opine that a 
particular defendant‟s crime was gang motivated, because the trier of fact is as 
competent as the witness to weigh the evidence and draw a conclusion from it.  
(Maj. opn., ante, at pp. 11-12, citing People v. Coffman and Marlow (2004) 34 
Cal.4th 1, 77, and People v. Prince (2007) 40 Cal.4th 1179, 1227.)  Nor does the 
majority dispute that the jury in this case must have understood the expert to be 
stating his opinion that, under the prosecution‟s version of the facts as set forth in 
the hypothetical, the hypothetical defendant‟s crime was gang motivated.  But the 
majority concludes the expert did not improperly invade the province of the jury 
and resolve any factual disputes because the jury would adopt the expert‟s opinion 
as its own only if it first found the prosecution‟s version of the facts to be true.  
(Maj. opn., ante, at pp. 12-13.) 
Although superficially plausible, the majority‟s explanation evades the 
central point that the expert told the jurors what inference concerning defendant‟s 
motive to draw in the event it did find the prosecution‟s evidence to be true.  If it 
 
3 
is accepted that expert opinion is not admissible if it consists of inferences and 
conclusions that can be drawn as easily by the trier of fact as by the witness (see, 
e.g., Amtower v. Photon Dynamics, Inc. (2008) 158 Cal.App.4th 1582, 1598; 
People v. Valdez (1997) 58 Cal.App.4th 494, 506), the question is whether the jury 
without expert assistance was competent to infer defendant‟s motive from the 
evidence.  We thus recognized in People v. Prince, supra, 40 Cal.4th at page 
1227:  “[A]n expert‟s opinion that a defendant is guilty is both unhelpful to the 
jury—which is equally equipped to reach that conclusion—and too helpful, in that 
the testimony may give the jury the impression that the issue has been decided and 
need not be the subject of deliberation.”  Similarly, in Summers v. A. L. Gilbert 
Co. (1999) 69 Cal.App.4th 1155, 1183, the court explained:  “ „[T]he rationale for 
admitting opinion testimony is that it will assist the jury in reaching a conclusion 
called for by the case.  “Where the jury is just as competent as the expert to 
consider and weigh the evidence and draw the necessary conclusions, then the 
need for expert testimony evaporates.”  [Citation.]‟  [Citations.]  In other words, 
when an expert‟s opinion amounts to nothing more than an expression of his or her 
belief on how a case should be decided, it does not aid the jurors, it supplants 
them.” 
Expert opinion is of course admissible when related to a subject that is 
sufficiently beyond common experience that the opinion of an expert would assist 
the trier of fact (Evid. Code, § 801), and testimony in the form of an opinion that is 
otherwise admissible is not objectionable because it embraces an ultimate issue 
(id., § 805).  This court long ago addressed the point in People v. Wilson (1944) 25 
Cal.2d 341, 349:  “There is no hard and fast rule that the expert cannot be asked a 
question that coincides with the ultimate issue in the case.  „We think the true rule 
is that admissibility depends on the nature of the issue and the circumstances of 
the case, there being a large element of judicial discretion involved. . . .  
 
4 
Oftentimes an opinion may be received on a simple ultimate issue, even when it is 
the sole one, as for example where the issue is the value of an article, or the sanity 
of a person; because it cannot be further simplified and cannot be fully tried 
without hearing opinions from those in better position to form them than the jury 
can be placed in.‟ ”  Thus, whether expert opinion on motive is admissible turns 
on whether it will be helpful to the jurors without unnecessarily supplanting them.  
In People v. Gardeley (1996) 14 Cal.4th 605, 617, we observed that the culture 
and practices of criminal street gangs are matters outside the common experience 
of  jurors,  justifying expert testimony to explain how certain activity might be 
gang related.  We did not in Gardeley hold that an expert in gangs and gang 
culture could also properly state his or her opinion that certain hypothetically 
stated activity was in fact gang motivated.  We stated, rather, that based on the 
expert‟s opinion that the hypothetical described a “ „classic‟ example of gang-
related activity” (id. at p. 619), “the jury could reasonably conclude” (ibid.) the 
attack was committed with the specific intent to promote or assist in gang criminal 
conduct, as required by Penal Code section 186.22, subdivision (b)(1).  The 
inference, in short, was for the jury to draw, based on the expert‟s explanation of 
gang practices and culture. 
While it is not inconceivable an expert opinion could in particular 
circumstances be needed to fully explain to the jury how a crime might be gang 
motivated, the majority does not consider the point in this case.  Instead, it broadly 
holds an expert‟s opinion on motive is admissible when stated in response to a 
hypothetical question rooted in the prosecution‟s evidence.  By failing to 
recognize that the admissibility of expert opinion is limited by the need for it, the 
 
5 
 
majority suggests that expert opinion on any issue is permissible when provided in 
response to a hypothetical question rooted in at least one party‟s evidence.  I am 
unwilling to subscribe to that rule.  
 
 
 
 
 
 
 
WERDEGAR, J. 
 
 
See next page for addresses and telephone numbers for counsel who argued in Supreme Court. 
 
Name of Opinion People v. Vang 
__________________________________________________________________________________ 
 
Unpublished Opinion 
Original Appeal 
Original Proceeding 
Review Granted XXX 195 Cal.App.4th 309 
Rehearing Granted 
 
__________________________________________________________________________________ 
 
Opinion No. S184212 
Date Filed: October 31, 2011 
__________________________________________________________________________________ 
 
Court: Superior 
County: San Diego 
Judge: Michael D. Wellington 
 
__________________________________________________________________________________ 
 
Counsel: 
 
John P. Dwyer, under appointment by the Supreme Court, for Defendant and Appellant. 
 
Edmund G. Brown and Kamala D. Harris, Attorneys General, Dane R. Gillette, Chief Assistant Attorney 
General, Gary W. Schons, Assistant Attorney General, Steve Oetting and Eric A. Swenson, Deputy 
Attorneys General, for Plaintiff and Respondent. 
 
 
 
 
 
 
 
 
 
Counsel who argued in Supreme Court (not intended for publication with opinion): 
 
John P. Dwyer 
Law Offices of John P. Dwyer 
601 Van Ness Avenue, Suite E-115 
San Francisco, CA  94102 
(415) 885-4451 
 
Steve Oetting 
Deputy Attorney General 
110 West A Street, Suite 1100 
San Diego, CA  92101 
(619) 645-2206