                            In the

United States Court of Appeals
              For the Seventh Circuit

No. 11-3716

U NITED S TATES OF A MERICA,
                                                Plaintiff-Appellee,
                                v.

R ONALD A. S EIVER,
                                            Defendant-Appellant.


            Appeal from the United States District Court
                  for the Central District of Illinois.
     No. 4:10-cr-40091-JES-JAG-1—James E. Shadid, Chief Judge.



     A RGUED A UGUST 7, 2012—D ECIDED A UGUST 28, 2012




 Before P OSNER, T INDER, and H AMILTON, Circuit Judges.
  P OSNER, Circuit Judge. The defendant pleaded guilty
to possession of child pornography and sexual exploita-
tion of a child, see 18 U.S.C. §§ 2252A(a)(5)(B), 2251(a),
and was sentenced to 420 months in prison. But he re-
served the right to appeal for the limited purpose
of challenging the legality of the search that had
yielded evidence that substantiated his guilt. The
appeal presents the recurrent issue of “staleness” as a
2                                               No. 11-3716

basis for concluding that a computer search warrant
was not supported by probable cause.
  The warrant affidavit said that law enforcement authori-
ties had discovered that a pornographic video which a 13-
year-girl had made of herself and uploaded to the
Internet had been downloaded to a computer at the de-
fendant’s home and that 16 still images from that
video—three of which were pornographic images of
the girl—had been uploaded from that computer to an
image-sharing website. A Facebook message with a link
to that website had been sent to the girl’s stepmother
from the same computer. She alerted the authorities, who
identified the computer’s Internet Protocol address
from the website. The address was registered to Ronald
Seiver, the defendant.
  He argues that there was no reason to believe that
seven months after he had uploaded child pornography
there would still be evidence of the crime on his com-
puter. Actually a search of his computer was
likely to find evidence of three crimes: receipt of child
pornography (the downloading of the pornographic
video); distribution (the uploading of the porno-
graphic images he obtained from the video); and posses-
sion (the storage of the pornography on his computer).
18 U.S.C. §§ 2252, 2252A. He was allowed to plead
guilty to only the last of these crimes (besides the sexual-
exploitation offense, which was unrelated to the video),
though there is no doubt that he committed the other
offenses as well. Even if he had deleted the child pornogra-
phy, a successful recovery of the images from his hard
No. 11-3716                                             3

drive by an FBI computer forensic expert would establish
that he had possessed them at one time, well within the
five-year statute of limitations.
  Nevertheless he contends that the facts that would
establish probable cause for a search of his computer
were “stale.” He adds that downloading a single video
and uploading still images derived from it could not
establish that he was a “collector” of child pornography
who could therefore be assumed to retain indefinitely
any illegal pornographic images that he had down-
loaded. The government concedes the premise that
“stale” computer contents are not a permissible basis for
a determination of probable cause but argues that a
law enforcement officer “could reasonably have
concluded that the [defendant], like the vast majority of
those who possess and distribute child pornography,
would still be in possession of those photographs
months later”—that he was, in other words, a “collector.”
  So the parties agree on the framework for analysis—the
importance of “staleness” and the importance to a deter-
mination of “staleness” of whether the suspect was a
“collector” and thus likely to have “retained” or “main-
tained” rather than “destroyed” the pornographic
images that he had acquired. The parties are faithfully
reciting terms appearing in a very large number of cases
concerning probable cause for a computer search. See,
e.g., United States v. Pappas, 592 F.3d 799, 803-04 (7th
Cir. 2010); United States v. Prideaux-Wentz, 543 F.3d
954, 958-59 (7th Cir. 2008); United States v. Estey, 595
F.3d 836, 839-40 (8th Cir. 2010); United States v. Lemon,
4                                                 No. 11-3716

590 F.3d 612, 614-16 (8th Cir. 2010); United States v. Potts,
586 F.3d 823, 830 (10th Cir. 2009); United States v. Paull, 551
F.3d 516, 522-23 (6th Cir. 2009); United States v. Morales-
Aldahondo, 524 F.3d 115, 119 (1st Cir. 2008); United States
v. Perrine, 518 F.3d 1196, 1205-06 (10th Cir. 2008); United
States v. Irving, 452 F.3d 110, 125 (2d Cir. 2006). But the
parties to this case, and the authors of the opinions in
the cases we’ve just cited (and in other cases that
we could cite involving computer searches for child
pornography), appear to be laboring under the misap-
prehension that deleting a computer file destroys it, so
that if the defendant had deleted the pornographic
images between their uploading to the Internet and the
search of his computer the search would not have
yielded up the images, or evidence of their earlier
presence in the computer, unless it’s a case in which
the defendant is a “collector” of child pornography
who decided to “keep” copies of the images that he’d
downloaded.
   The concern with “staleness” versus freshness and
“collecting” versus destroying reflects a misunder-
standing of computer technology. (A number of cases,
however, though none in our court, reflect the correct
understanding. See, e.g., United States v. Allen, 625 F.3d
830, 843 (5th Cir. 2010); United States v. Richardson, 607
F.3d 357, 370-71 (4th Cir. 2010); United States v. Lewis,
605 F.3d 395, 402 (6th Cir. 2010).) When you delete a file,
it goes into a “trash” folder, and when you direct the
computer to “empty” the trash folder the contents of
the folder, including the deleted file, disappear. But the
file hasn’t left the computer. The trash folder is a waste-
No. 11-3716                                                5

paper basket; it has no drainage pipe to the outside. The
file seems to have vanished only because the computer
has removed it from the user interface and so the user
can’t “see” it any more. Virginia M. Kendall & T. Markus
Funk, Child Exploitation and Trafficking 275-76 (2012);
United States v. Flyer, 633 F.3d 911, 918 (9th Cir. 2011);
United States v. Gourde, 440 F.3d 1065, 1071 (9th Cir.
2006) (en banc). But it’s still there, and normally is re-
coverable by computer experts until it’s overwritten
because there is no longer unused space in the com-
puter’s hard drive.
  How soon a file will be overwritten depends on a
number of factors: whether the user is computer savvy
and has installed a program that accelerates the normal
overwriting of deleted data, how often he saves new files
to his hard drive, the capacity of the hard drive, and how
the computer’s file system allocates new files. But we
know that the FBI routinely extracts incriminating
deleted files from hard drives, usually without difficulty.
See, e.g., FBI, “Occupational Technology—Overview,”
www.fbi.gov/about-us/otd/overview (all websites visited
Aug. 15, 2012); U.S. Dep’t of Justice, “Forensic Examination
of Digital Evidence: A Guide for Law Enforcement” 16,
21, 39 (April 2004), www.ncjrs.gov/pdffiles1/nij/199408.pdf;
John Patzakis, “Computer Forensics as an Integral Compo-
nent of the Information Security Enterprise” 3 (Guidance
Software 2003), http://faculty.usfsp. edu/gkearns/Articles_
Fraud/computerforensics.pdf; Wade Davies, “Computer
Forensics: How to Obtain and Analyze Electronic Evi-
dence” The Champion, June 2003, p. 34, www.nacdl.org/
Champion.aspx?id=807.
6                                                No. 11-3716

  And since a deleted file is not overwritten all at once, it
may be possible to reconstruct it from the bits of data
composing it (called “slack data”), which are still retriev-
able because they have not yet been overwritten even if
overwriting has begun. Before a file is deleted, the file
system marks it as unavailable to be overwritten. Once
it is deleted, its data are no longer protected against
being overwritten, but the file system won’t necessarily
overwrite it all at once, and if it’s only partially overwrit-
ten computer experts can recover the portion of the data
that has not been overwritten, or at least can match it to
images they obtained from (as in this case) a website, to
verify that the images were once in the computer’s hard
drive and thus had been possessed. See Michele C.S.
Lange & Kristin M. Nimsger, Electronic Evidence and
Discovery: What Every Lawyer Should Know Now 235
(2d ed. 2009). Although a savvy computer user can
as we said direct his computer to ensure quick (even
instantaneous) overwriting, the default settings on stan-
dard operating systems don’t do this.
  “Staleness” is highly relevant to the legality of a search
for a perishable or consumable object, like cocaine, but
rarely relevant when it is a computer file. Computers
and computer equipment are “not the type of evidence
that rapidly dissipates or degrades.” United States v.
Vosburgh, 602 F.3d 512, 529 (3d Cir. 2010). Because of
overwriting, it is possible that the deleted file will no
longer be recoverable from the computer’s hard drive.
And it is also possible that the computer will have been
sold or physically destroyed. And the longer the
interval between the uploading of the material sought
as evidence and the search of the computer, the greater
No. 11-3716                                               7

these possibilities. But rarely will they be so probable as
to destroy probable cause to believe that a search
of the computer will turn up the evidence sought; for
probable cause is far short of certainty—it “requires only
a probability or substantial chance of criminal activity,
not an actual showing of such activity,” Illinois v. Gates,
462 U.S. 213, 244 n. 13 (1983), and not a probability
that exceeds 50 percent (“more likely than not”), either.
Hanson v. Dane County, 608 F.3d 335, 338 (7th Cir. 2010).
Notice too that even if the computer is sold, if the
buyer can be found the file will still be on the
computer’s hard drive and therefore recoverable,
unless it’s been overwritten. The search warrant will
have designated the premises where the computer was
expected to be found, and though a computer sold by
the occupant will obviously no longer be there, evidence
may be found there of the buyer’s identity.
  Computer procedures such as “defragmenting,” “wip-
ing,” and creating “garbage files” can make deleted
computer files very difficult or even impossible to re-
cover. Lange & Nimsger, supra, at 221-24. And encryption
may hide files remaining on the hard drive so effectively
as to thwart their recovery by computer experts. Kendall
& Funk, supra, at 167. Software that wipes the hard drive
or overwrites deleted files with garbage data can be
bought on line. But it appears that few consumers of
child pornography (the producers may be more savvy)
understand well enough how their computer’s file
system works to grasp the importance of wiping or
overwriting their deleted pornographic files or encrypting
them securely if they want to avoid leaving recoverable
8                                              No. 11-3716

evidence of child pornography in their computer after
they’ve deleted it. Anyway this way of thwarting
a search has nothing to do with staleness. A child pornog-
rapher who wants to render computer files nonrecov-
erable will first download those he wants to keep to
a DVD, which can be hidden outside his home, and
then either destroy the computer and get a new, “clean”
one, or take steps to assure the complete overwriting of
the contents of his hard drive. Nevertheless, despite
the availability of software for obliterating or concealing
incriminating computer files, the use of such software
“is surprisingly rare.” Kendall & Funk, supra, at 276.
  No doubt after a very long time, the likelihood that
the defendant still has the computer, and if he does that
the file hasn’t been overwritten, or if he’s sold it that
the current owner can be identified, drops to a level at
which probable cause to search the suspect’s home for
the computer can no longer be established. But seven
months is too short a period to reduce the probability
that a computer search will be fruitful to a level at
which probable cause has evaporated.
  Some cases, illustrated by United States v. Allen, supra,
625 F.3d at 843, say it’s important that the search
warrant affidavit apprise the magistrate asked to issue
the warrant that deleted files are recoverable. That may
be prudent, because some magistrates may not know
a great deal about computers, but it shouldn’t be
required to make the warrant valid; it is or should
be common knowledge.
  Now it is true that after deleting a file and emptying
the trash bin containing it, a computer owner who is not
No. 11-3716                                                   9

technologically sophisticated no longer “possesses” the
file in a meaningful sense, see, e.g., United States v. More-
land, 665 F.3d 137, 152 (5th Cir. 2011), and the crime of
which the defendant was committed requires knowing
possession. Had the defendant deleted the incriminating
files (and emptied his trash folder with those files in it),
he would no longer have knowingly possessed them
if, as in Moreland, he could no longer access them
because he lacked the software that he would have
needed to be able to recover them from the hard drive’s
slack space. United States v. Flyer, supra, 633 F.3d at 918-20.
But this need not have eliminated probable cause for
a search of his computer unless the statute of limitations
on possession had expired by the time the search was
conducted, which it had not done in this case. See
United States v. Kain, 589 F.3d 945, 948-50 (8th Cir. 2009).
  The most important thing to keep in mind for future
cases is the need to ground inquiries into “staleness” and
“collectors” in a realistic understanding of modern com-
puter technology and the usual behavior of its users.
Only in the exceptional case should a warrant to search
a computer for child pornography be denied on either
of those grounds (there are of course other grounds
for denial). But future changes in computer technology
may alter this conclusion, and judges as well as law
enforcers must be alert to that possibility as well.
                                                   A FFIRMED.



                            8-28-12
