In the
United States Court of Appeals
For the Seventh Circuit
No. 11-2894
U NITED S TATES OF A MERICA,
Plaintiff-Appellee,
v.
C LACY W ATSON H ERRERA,
Defendant-Appellant.
Appeal from the United States District Court
for the Northern District of Illinois, Eastern Division.
No. 01 CR 1098-1—Rebecca R. Pallmeyer, Judge.
A RGUED S EPTEMBER 28, 2012—D ECIDED JANUARY 9, 2013
Before P OSNER, R OVNER, and SYKES, Circuit Judges.
P OSNER, Circuit Judge. Two years ago, in response to
a petition for a writ of mandamus filed by the govern-
ment during the criminal trial of the defendant on drug
charges, we ordered the district court to admit into evi-
dence an exhibit labeled “Roberson Seizure 2”; to allow
the government to recall Stephen Koop to testify at
trial about the recovery of latent fingerprints from that
exhibit; and to allow testimony regarding comparison of
2 No. 11-2894
the latent prints with patent fingerprints known to be the
defendant’s. In re United States, 614 F.3d 661 (7th Cir.
2010). The judge had excluded the exhibit and related
testimony because he suspected, though on the most
tenuous of grounds, that the government had tampered
with the fingerprint evidence. He threatened to grant
the defendant’s request for a mistrial on the ground of
prosecutorial misconduct that was (the judge believed)
intended to avert a likely acquittal, a ground that if sus-
tained would have barred any further prosecution of the
defendant as placing him in double jeopardy. Oregon v.
Kennedy, 456 U.S. 667, 679 (1982); United States v. Catton, 130
F.3d 805, 807-08 (7th Cir. 1997); see also United States v.
Buljubasic, 808 F.2d 1260, 1265 (7th Cir. 1987). We also
ordered the case reassigned to another district judge.
This was done and the trial, which had been interrupted
by the mandamus proceeding, resumed, and ended
shortly in the conviction of the defendant. The judge
sentenced him to 340 months in prison for a variety of
drug-related offenses. He appeals.
Many of his arguments repeat ones he made in the
mandamus proceeding. (In effect he is asking us to
rehear our previous decision—two years after the dead-
line for asking for rehearing expired.) The only such
argument that we didn’t discuss is based on Will v.
United States, 389 U.S. 90, 96-97 (1967), which forbids
the use of mandamus as a substitute for an appeal that
is forbidden—and the government is not permitted to
appeal an evidentiary ruling in a criminal case once
the trial has begun. 18 U.S.C. § 3731. But the Court in
Will held only that the court of appeals hadn’t explained
No. 11-2894 3
why the district court’s ordering the government to
give the defendant a bill of particulars was so
“seriously disruptive of the efficient administration of
criminal justice in the Northern District of Illinois” as to
warrant mandamus. 389 U.S. at 104. The district judge’s
order in the present case was no run-of-the-mill mistaken
procedural or evidentiary ruling. The order seriously
disrupted the prosecution’s case, and did so, as we
are about to show, on the basis of utterly baseless but
damaging imputations of grave (criminal, really) pros-
ecutorial misconduct; involved the flouting of gov-
erning precedents; and would probably have resulted
in a groundless acquittal. The order thus warranted
correction by mandamus. See United States v. Vinyard, 539
F.3d 589, 591-92 (7th Cir. 2008).
The chain of events that culminated in the mandamus
proceeding had begun with the district judge’s decision
to exclude evidence that two of the defendant’s finger-
prints had been recovered from a bag of heroin wrapped
in tape and further encased in condoms and found in
a drug courier’s rectum. The heroin had been removed
from the bag and placed in an evidence bag and then
both it and the packaging (the tape and condoms) had
been placed in another evidence bag and it was this
second exhibit that was at issue. The district judge’s
ground for excluding it was his belief that the govern-
ment hadn’t adequately demonstrated the requisite
“chain of custody”—hadn’t demonstrated that there
had been no opportunity to tamper with or otherwise
mishandle the evidence between the time it was
obtained and the trial. The judge made this ruling in the
4 No. 11-2894
face of the government’s having offered ten witnesses
to establish that the chain of custody had remained intact.
The judge was disturbed because the exhibit had,
according to an evidence log sheet, gained 20 grams in
weight between May and September 2001. (Yet he
attached no significance to its having gained 190 grams
between September 2001 and the trial.) He thought
the weight gain might have been attributable to fed-
eral officers’ pressing a piece of adhesive tape con-
taining the defendant’s fingerprints (obtained else-
where) onto the packaging of the heroin. That suspicion
grew into a conviction, for which there was no rational
basis, that government lawyers had lied about the chain
of custody. To no avail the government explained that
the reason for the increase in weight was that the bag
with the fingerprints, after being opened so that the
presence and amount of the illegal drug contained in
it could be verified, and later closed up again, had been
weighed together with other bags. The reported weight
was the weight of the package containing all the
bags, and thus there were more bags in it. Obviously
the package would not have gained 210 grams (20 +
190)—almost half a pound—from replacing a piece of the
tape in which one of the bags was wrapped by a piece
of tape containing the defendant’s fingerprints.
The judge acknowledged that his supposition of tam-
pering was “speculative.” That was an understatement.
For among other things the defendant had not been
extradited to the United States until long after the
alleged tampering, and until he was extradited the gov-
No. 11-2894 5
ernment did not have a set of fingerprints known to be
his. And no one has explained how fingerprints on
another piece of material could have been transferred
to the adhesive side of the tape, which was where they
were found. It’s one thing to press your finger on the
adhesive side of a tape and remove the finger, leaving
a print, but another thing to press a piece of paper con-
taining your fingerprint on the adhesive side of
the tape—try removing the paper without destroying
the print.
The defendant’s petition, and amended petition, for
rehearing did not defend the judge’s conjecture that
the weight discrepancy indicated tampering. We con-
cluded that while the defendant could argue at trial
that the jury should disregard the fingerprint evidence,
there was no justification for excluding it in advance
of trial on the “speculative” ground excogitated by
the judge. Once the government presents evidence, as
it did here (remember the ten witnesses), that adequate
precautions had been taken to preserve the evidence
challenged by the defendant, it has established admissi-
bility, though at trial the defendant can challenge the
adequacy of the precautions and present evidence of
tampering. United States v. Lee, 502 F.3d 691, 697-98
(7th Cir. 2007); United States v. Kelly, 14 F.3d 1169, 1175 (7th
Cir. 1994); United States v. Brumfield, 686 F.3d 960, 965
(8th Cir. 2012); see also Melendez-Diaz v. Massachusetts,
557 U.S. 305, 311 n. 1 (2009). And that means by the
way that even if our mandamus order was ultra vires
it didn’t undermine the fairness of the trial or the justice
of the defendant’s conviction. The fingerprint evidence
6 No. 11-2894
should not have been excluded, and once admitted con-
firmed his guilt. We take up at the end of our opinion
the defendant’s distinct argument that the reassignment
of the case to another judge prejudiced the jury, and
show that that argument has no merit either.
The fresh issue relating to the fingerprint evidence
is whether the prints of two fingers found on the
adhesive tape were the defendant’s. They were latent
rather than patent fingerprints. Patent fingerprints are
made by pressing a fingertip covered with ink on a
white card or similar white surface, and are visible.
Latent fingerprints are prints, usually invisible, left on a
smooth surface when a person touches it with a finger
or fingers. Laboratory techniques are employed to make
a latent fingerprint visible so that it can be compared
with other fingerprints. The latent prints on the adhesive
tape on the bag of heroin in this case were found by
a fingerprint examiner to match the defendant’s patent
prints made in the course of the criminal investigation,
and the government therefore offered the match as evi-
dence of the defendant’s participation in the drug ring.
The defendant argues that methods of matching latent
prints with other latent prints or with patent prints
have not been shown to be reliable enough to be
admissible as evidence under the standard for
reliability set forth in Fed. R. Evid. 702, 703; Daubert v.
Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 592-93
(1993); and Kumho Tire Co. v. Carmichael, 526 U.S. 137,
149 (1999).
The method the examiner used is called ACE-V and
is the standard method for determining whether two
No. 11-2894 7
fingerprints are from the same person. See Scientific
Working Group on Friction Ridge Analysis, Study and
Technology, “Standards for Examining Friction Ridge
Impressions and Resulting Conclusions,” Sept. 13, 2011,
www.swgfast.org/documents/examinations-conclusions/
111026_Examinations-Conclusions_1.0.pdf (visited Jan. 4,
2013); Michele Triplett & Lauren Cooney, “The Etiology
of ACE-V and Its Proper Use: An Exploration of the
Relationship Between ACE-V and the Scientific Method
of Hypothesis Testing,” 56 J. Forensic Identification 345, 346
(2006). The defendant is therefore mounting a frontal
assault on the use of fingerprint evidence in litigation, an
attack the courts have frequently rebuffed. See, e.g.,
United States v. Havvard, 260 F.3d 597, 601 (7th Cir. 2001);
United States v. George, 363 F.3d 666, 672-73 (7th Cir.
2004); United States v. Crisp, 324 F.3d 261, 268-70 (4th
Cir. 2003); United States v. Mitchell, 365 F.3d 215, 235-
46 (3d Cir. 2004).
ACE-V is an acronym for analysis, comparison, evalua-
tion, and verification, and has been described as follows:
The process begins with the analysis of the unknown
friction ridge print (now often a digital image of
a latent print). Many factors affect the quality and
quantity of detail in the latent print and also
introduce variability in the resulting impression . . . . If
the examiner deems that there is sufficient detail
in the latent print (and the known prints), the com-
parison of the latent print to the known prints begins.
Visual comparison consists of discerning, visually
“measuring,” and comparing—within the comparable
areas of the latent print and the known prints—the
8 No. 11-2894
details that correspond. The amount of friction
ridge detail available for this step depends on the
clarity of the two impressions. The details observed
might include the overall shape of the latent print,
anatomical aspects, ridge flows, ridge counts, shape of
the core, delta location and shape, lengths of the
ridges, minutia location and type, thickness of the
ridges and furrows, shapes of the ridges, pore
position, crease patterns and shapes, scar shapes,
and temporary feature shapes (e.g., a wart).
At the completion of the comparison, the examiner
performs an evaluation of the agreement of the
friction ridge formations in the two prints and evalu-
ates the sufficiency of the detail present to establish
an identification (source determination). Source de-
termination is made when the examiner concludes,
based on his or her experience, that sufficient
quantity and quality of friction ridge detail is in
agreement between the latent print and the known
print. Source exclusion is made when the process
indicates sufficient disagreement between the latent
print and known print. If neither an identification
nor an exclusion can be reached, the result
of the comparison is inconclusive. Verification occurs
when another qualified examiner repeats the observa-
tions and comes to the same conclusion, although
the second examiner may be aware of the conclu-
sion of the first.
National Research Council of the National Academy of
Sciences, Strengthening Forensic Science in the United States:
A Path Forward 137-38 (2009).
No. 11-2894 9
The methodology requires recognizing and categorizing
scores of distinctive features in the prints, see Davide
Maltoni et al., Handbook of Fingerprint Recognition 97-101
(2d ed. 2009); Federal Bureau of Investigation, The
Science of Fingerprints: Classification and Uses 5-86 (2006),
and it is the distinctiveness of these features, rather
than the ACE-V method itself, that enables expert finger-
print examiners to match fingerprints with a high
degree of confidence. That’s not to say that fingerprint
matching (especially when it involves latent finger-
prints, as in this case) is as reliable as DNA evidence, for
example. Forensic DNA analysis involves comparing a
strand of DNA (the genetic code) from the suspect with
a strand of DNA found at the crime scene. The
comparison is done with scientific instruments and deter-
mines whether the segments are chemically identical.
Errors are vanishingly rare provided that the strands
of code are reasonably intact. As we explained in
United States v. Ford, 683 F.3d 761, 768 (7th Cir. 2012),
What is involved, very simply, in forensic DNA
analysis is comparing a strand of DNA (the genetic
code) from the suspect with a strand of DNA found at
the crime scene. See “DNA Profiling,” Wikipedia,
http://en.wikipedia.org/wiki/DNA_profiling (visited
May 31, 2012). Comparisons are made at various
locations on each strand. At each location there is
an allele (a unique gene form). In one location, for
example, the probability of a person’s having a par-
ticular allele might be 7 percent, and in another
10 percent. Suppose that the suspect’s DNA and the
DNA at the crime scene contained the same alleles
10 No. 11-2894
at each of the two locations. The probability that
the DNA was someone else’s would be 7 percent if the
comparison were confined to the first location, but
only .7 percent (7 percent of 10 percent) if the com-
parison were expanded to two locations, because
the probabilities are independent. Suppose identical
alleles were found at 10 locations, which is what
happened in this case; the probability that two
persons would have so many identical alleles, a proba-
bility that can be computed by multiplying together
the probabilities of an identical allele at each
location, becomes infinitesimally small—in fact 1 in
29 trillion, provided no other comparisons reveal
that the alleles at the same location on the two
strands of DNA are different. This is the same proce-
dure used for determining the probability that a
perfectly balanced coin flipped 10 times in a row will
come up heads all 10 times. The probability is .51 0 ,
which is less than 1 in 1000.
Chemical tests can determine whether two alleles are
identical, but a fingerprint analyst must visually
recognize and classify the relevant details in the latent
print—which is difficult if the print is incomplete or
smudged. “[T]he assessment of latent prints from crime
scenes is based largely on human interpretation. . . . [T]he
process does not allow one to stipulate specific measure-
ments in advance, as is done for a DNA analysis. More-
over, a small stretching of distance between two finger-
print features, or a twisting of angles, can result from
either a difference between the fingers that left the
prints or from distortions from the impression process.”
National Research Council, supra, at 139.
No. 11-2894 11
Matching latent fingerprints is thus a bit like an
opinion offered by an art expert asked whether an un-
signed painting was painted by the known painter of
another painting; he makes or rejects a match on the
basis of visual evidence. Eyewitness evidence is similar.
The eyewitness saw the perpetrator of a crime. His recol-
lection of the perpetrator’s appearance is analogous to
a latent fingerprint. He sees the defendant at the
trial—that sighting is analogous to a patent fingerprint.
He is asked to match his recollection against the court-
room sighting—and he is allowed to testify that the
defendant is the perpetrator, not just that there is a close
resemblance. A lineup, whether photo or in-person, is
a related method of adducing matching evidence, as
is handwriting evidence.
Matching evidence of the kinds that we’ve just
described, including fingerprint evidence, is less
rigorous than the kind of scientific matching involved
in DNA evidence; eyewitness evidence is not scientific
at all. But no one thinks that only scientific evidence
may be used to convict or acquit a defendant. The in-
creasingly well documented fallibility of eyewitness
testimony, see Elizabeth F. Loftus et al., Eyewitness Testi-
mony: Civil and Criminal (4th ed. 2007); United States v.
Ford, supra, 683 F.3d at 764-66, has not banished it from
criminal trials. Perry v. New Hampshire, 132 S. Ct. 716,
728 (2012).
Evidence doesn’t have to be infallible to be probative.
Probability of guilt is a function of all the evidence in
a case, and if items of evidence are independent of one
12 No. 11-2894
another in the sense that the truth of any one item is
not influenced by the truth of any other, the probability
of guilt may be much higher if there is evidence
from many independent sources (several eyewitnesses,
an eyewitness plus fingerprints, etc.) than it would be
were there only the evidence of one eyewitness, say. If
“the prosecution submits three items of evidence of the
defendant’s guilt (and the defendant submits no
evidence of his innocence), and the probability that item 1
is spurious is 10 percent, the probability that item 2
is spurious is also 10 percent, and likewise item 3 [,
then the] probability that all three are spurious (assuming
that the probabilities are independent—that is, that
the probability that one piece of evidence is spurious
does not affect the probability that another is), and there-
fore that the defendant should be acquitted, is only one
in a thousand (.1 x .1 x .1).” United States v. Williams,
698 F.3d 374, 379 (7th Cir. 2012).
The defendant intimates that any evidence that
requires the sponsorship of an expert witness, as finger-
print evidence does, must be found to be good science
before it can be admitted under the doctrine of the
Daubert case and Rules 702 or 703 of the Federal Rules
of Evidence. But expert evidence is not limited to “scien-
tific” evidence, however such evidence might be de-
fined. Kumho Tire Co. v. Carmichael, supra, 526 U.S. at 150-51;
Tuf Racing Products, Inc. v. American Suzuki Motor
Corp., 223 F.3d 585, 591 (7th Cir. 2000). It includes any
evidence created or validated by expert methods
and presented by an expert witness that is shown to
be reliable. In a case involving an alleged forgery of a
No. 11-2894 13
painting, there might be expert scientific evidence based
on tests of the age of the canvas or paint; but there
might also be expert evidence, offered by a dealer or art
historian or other art expert, on the style of a particular
artist. That evidence would be the expert’s opinion,
based on comparison with other paintings, of the genuine-
ness of the painting alleged to be a forgery. See, e.g.,
Levin v. Dalva Brothers, Inc., 459 F.3d 68, 78-79 (1st Cir.
2006); United States v. Tobin, 576 F.2d 687, 690-91, 693
(5th Cir. 1978).
Fingerprint experts such as the government’s witness
in this case—who has been certified as a latent print
examiner by the International Association for Identifica-
tion, the foremost international fingerprint organiza-
tion (there are only about 840 IAI-certified latent
examiners in the world, out of 15,000 total examin-
ers)—receive extensive training; and errors in finger-
print matching by expert examiners appear to be
very rare. Of the first 194 prisoners in the United States
exonerated by DNA evidence, none had been convicted
on the basis of erroneous fingerprint matches, whereas
75 percent had been convicted on the basis of mistaken
eyewitness identification. Greg Hampikian et al.,
“The Genetics of Innocence: Analysis of 194 U.S. DNA
Exonerations,” 12 Annual Rev. of Genomics and Human
Genetics 97, 106 (2011). The probability of two people in
the world having identical fingerprints is not known,
but it appears to be extremely low. Steven M. Stigler,
“Galton and Identification by Fingerprints,” 140 Genetics
857, 858 (1995); David A. Stoney & John I. Thornton,
14 No. 11-2894
“A Critical Analysis of Quantitative Fingerprint Indi-
viduality Models,” 31 J. of Forensic Sciences 1187 (1986).
The great statistician Francis Galton estimated the proba-
bility as 1 in 64 billion. Galton, Finger Prints 110 (1892);
Stigler, supra at 858. That was not an estimate of the
probability of a mistaken matching of a latent to a
patent or another latent fingerprint. Yet errors in such
matching appear to be very rare, though the matching
process is judgmental rather than scientifically rigorous
because it depends on how readable the latent finger-
print is and also on how distorted a version of the
person’s patent fingerprint it is. Examiners’ training
includes instruction on how to determine whether a
latent print contains enough detail to enable a reliable
matching to another print. Ultimately the matching
depends on “subjective judgments by the examiner,”
National Research Council, supra, at 139, but responsible
fingerprint matching is admissible evidence, in general
and in this case.
The other issues presented by the appeal that merit
discussion arise from the interruption of the trial by the
mandamus proceeding and the resulting reassignment
of the case to a different district judge. The con-
sequence was an eleven-day hiatus in the trial. The defen-
dant argues that when the trial resumed, the jurors,
remembering the skeptical remarks that the original
judge had made about the government’s evidence, must
have thought that he had been “punished” for siding
with the defendant by being removed and therefore
that the jury should convict. That is unpersuasive con-
No. 11-2894 15
jecture. Because of sickness most commonly, but some-
times for other reasons, such as belated discovery of
a ground for recusal, a judge is sometimes replaced
during a trial and when that happens the new judge
tells the jury that such replacements happen oc-
casionally and the jurors are not to worry about the
change in judges or speculate about the reason for it.
The new judge in this case didn’t explain the cause of
the delays but did say:
It is very important for me to emphasize this instruc-
tion, that however you may feel about the delays
in this case, you are not to hold those feelings
against anybody in this courtroom . . . . In fact, I am
going to instruct you right now that you not
speculate about the causes or reasons for the delays
at all . . . . To the extent that you have been told or
you have come to believe that the delays are
somehow the fault of the government or the fault of
the defense counsel, I am instructing you that you
put those concerns out of your mind completely . . . .
At the end of this case, we will not be asking you, did
the trial go smoothly? And if not, whose fault was it?
That will not be a question you will be asked to con-
sider. The only question you will be asked to consider
at the conclusion of this case is, did the government
meet its burden of proof? That’s the only question.
And concerns about delays are not to be in your
mind at all . . . . From time to time there are
reasons that we have to interrupt the smooth progress
of a trial. It’s happened to me before. This was one of
those occasions . . . . Your consideration of the
16 No. 11-2894
evidence should not be influenced in any way by
any assumptions you may have made or any conclu-
sions you may have drawn about delays.
There is no history of which we’re aware of
miscarriages of justice resulting because juries draw
erroneous inferences from the replacement of a judge.
See United States v. Gayles, 1 F.3d 735, 738 (8th Cir. 1993);
United States v. LaSorsa, 480 F.2d 522, 531 (2d Cir. 1973).
The defendant complains that the new judge pres-
sured the jury to complete its deliberations in a day
and that with more time it might have acquitted him.
There is no evidence to support that accusation of a
judge noted for her patience. The first judge had assured
the jury that the trial would not interfere with any of
the jurors’ vacation schedules. When trial resumed on
August 2 the jury was down to 12 because one of the
two alternates had been excused and the other had re-
placed a juror who had been excused. One of the
remaining jurors had long-standing vacation plans for
August 5, and the original judge had (with the govern-
ment’s consent) assured her when the government
sought mandamus and the trial was adjourned that
she would not need to show up on or after that date.
When the trial resumed, another juror asked in open
court what the jury should do in light of the possibility
that the juror with vacation plans would leave before
the trial ended. In response, and without objection by
the defendant’s lawyer, the judge said “we can’t proceed”
with fewer than 12 jurors. That was true (since the
parties would not stipulate to a jury of 11, see Fed. R. Crim.
No. 11-2894 17
P. 23(b)(2)), though what was also true but she rightly
did not say, because it would have sown confusion, is
that while the trial could not continue without 12 jurors,
if once the jury retired for its deliberations one of the
jurors then decamped the judge could allow the
remaining 11 to render a verdict even without the law-
yers’ consent. Fed. R. Crim. P. 23(b)(3).
August 4 turned out to be the last day of the trial.
Closing arguments and the reading of the instructions
to the jury took until the afternoon. The jury retired to
consider its verdict at about 3:45 and returned 7 hours
later with a verdict of guilty on eight counts and not
guilty on the remaining six. The defendant argues that
the jurors had rushed to complete their deliberations,
knowing there would not be 12 jurors the next day.
Given the strength of the government’s case and the
length of the jury’s deliberations, and the fact that
there was only one defendant and that the jury
acquitted him on some counts, it is unlikely that even
if they hadn’t been expecting to lose the twelfth juror
the next day, the jurors would have taken more time
to deliberate than they did, though they might have
broken at dinner time and resumed the following morn-
ing. The judge did not, as in the cases that the defendant
cites to us, United States v. Blitch, 622 F.3d 658, 670 (7th
Cir. 2010), and United States v. Chaney, 559 F.2d 1094, 1098
(7th Cir. 1977), set a deadline, either explicit or implicit,
for the jury’s deliberations. On the contrary, after instruct-
ing the jury, and only moments before the jury left
the courtroom to deliberate, the judge told them:
“I think I mentioned earlier that from this point on, the
18 No. 11-2894
schedule is up to you. I realize [by] the way that the trial
has been bumpy, and I will make every effort to accom-
modate your schedule from this moment on, whatever
your decisions are. I appreciate your time. I think all of
us do. You are excused to deliberate on your verdict.”
That was the opposite of pressuring the jury to complete
its deliberations in a day. The jurors were unlikely to
feel rushed when the judge had gone out of her way to
tell them that she would make every effort to accom-
modate their schedules. Had the jurors been unable to
agree on a verdict on August 4, the foreman would have
told the judge that they couldn’t reach a verdict and she
would have either discharged them and declared a
mistrial or allowed the 11 remaining jurors to return
the next day and deliberate.
When the jury retired to deliberate, knowing that one
juror would leave on vacation the next day and perhaps
believing that 12 jurors had to be present to render a
verdict, no juror asked the judge a question such as:
“Does this mean we must render a verdict by the end of
the day or can we just report our inability to reach
a verdict?” Or: “What if we can’t complete our delibera-
tions by the end of the day?” Such questions would
have flagged concerns that the judge would doubtless
have addressed. No questions were asked. That
suggests that the jurors were not concerned that the
trial might end without a verdict unless they rushed
their deliberations.
A FFIRMED.
1-9-13