In the

    United States Court of Appeals
                 For the Seventh Circuit
                     ____________________

No. 17-2665
KATRINA WALKER,
                                                  Plaintiff-Appellant,
                                 v.

CARL WEATHERSPOON, et al.,
                                               Defendants-Appellees.
                     ____________________

         Appeal from the United States District Court for the
           Northern District of Illinois, Eastern Division.
             No. 12 C 8571 — Andrea R. Wood, Judge.
                     ____________________

     ARGUED APRIL 24, 2018 — DECIDED AUGUST 13, 2018
                 ____________________

   Before BAUER, EASTERBROOK, and KANNE, Circuit Judges.
    EASTERBROOK, Circuit Judge. On March 31, 2016, when this
suit was three and a half years old, the district court entered
an order granting summary judgment to defendants “[f]or
the reasons stated in the Memorandum Opinion and Order
to follow”. More than 16 months passed before the judge re-
leased her opinion, 

(N.D. Ill.
Aug. 15, 2017), and plaintiff appealed that day. A judgment
under Fed. R. Civ. P. 58 was entered on August 16.
2                                                 No. 17-2665

   This appeal came many months too late under Fed. R.
App. P. 4(a)(7)(A)(ii), which says that a judgment is deemed
to be entered on the earlier of the Rule 58 judgment or 150
days after a dispositive order is entered on the civil docket.
Until Rule 4(a)(7)(A)(ii) was adopted in 2002 the losing side
always could wait for the entry of the formal judgment. See
United States v. Indrelunas, 

(1973); Carter v.
Hodge, 

, 919–20 (7th Cir. 2013). The new rule su-
persedes Indrelunas by deeming the judgment to have been
entered 150 days after a dispositive order that does not
amount to a proper judgment.
    A district judge who announces a final decision yet post-
pones issuing the opinion sets a trap for the losing side, be-
cause a plan to provide an explanation does not delay the
date of decision. See United States v. Bradley, 

,
394 (2d Cir. 2018). Most litigants who represent themselves,
and many lawyers, are unaware of Rule 4(a)(7)(A)(ii) and
think that they can wait for the entry of judgment. Litigants
can protect themselves—for example, the loser may file a no-
tice of appeal and ask the court of appeals to defer briefing
until the district court has released its opinion. But judges
should not expose litigants to the risk that they will miss the
need for self-protective steps. See, e.g., Otis v. Chicago, 

, 1163, 1167–68 (7th Cir. 1994) (en banc). Except
when there is a need for speedy announcement of the out-
come, the opinion should accompany the decision. This is
not a suit in which rapid decision was essential, so a de-
ferred opinion was unjustified. And when there is a justifica-
tion for announcing a decision in advance of an opinion, is-
suing the opinion should be the district judge’s top priority.
Deferring the opinion until after the time allowed by Rule
No. 17-2665                                                             3

4(a)(7)(A)(ii) is never appropriate, as it can spell disaster for
a litigant not versed in the appellate rules.
   As it happens, however, this appeal has been saved by
the fact that until recently everyone missed the significance of
Rule 4(a)(7)(A)(ii).
    The only jurisdictional requirement is the need for an
appeal within 30 days of the judgment or an extension. See
28 U.S.C. §2107; Bowles v. Russell, 

(2007). Hamer
v. Neighborhood Housing Services of Chicago, 

(2017), tells us that supplemental or implementing provi-
sions in the Rules of Appellate Procedure are not jurisdic-
tional. Hamer concerned Rule 4(a)(5)(C); its holding applies
equally to Rule 4(a)(7)(A)(ii).
   Although the Rules of Appellate Procedure are not juris-
dictional, they remain mandatory. We must apply them if
properly invoked. The “properly invoked” qualifier is im-
portant, for a litigant may waive or forfeit the benefit of the-
se rules. We held on remand in Hamer that the appellees
waived the benefit of Rule 4(a)(5)(C) by representing in their
docketing statement that the appeal was timely. Hamer v.
Neighborhood Housing Services of Chicago, No. 15-3764 (7th Cir.
July 30, 2018), slip op. 4–8. Appellees in this case did not do
that, but they came close—close enough to forfeit their rights
under Rule 4(a)(7)(A)(ii).
   The jurisdictional section of appellees’ brief in this court
says (some citations omitted):
   On March 31, 2016, the district court issued a minute order
   granting defendants’ motion for summary judgment on all of
   Walker’s claims. On August 15, 2017, the district court issued its
   memorandum opinion and order setting forth the reasons for its
   grant of summary judgment in defendants’ favor. On the same
4                                                            No. 17-2665

    day, Walker filed her notice of appeal. The judgment was en-
    tered on August 16, 2017. A premature notice of appeal is treated
    as filed on the date the judgment is entered. Fed. R. App. P.
    4(a)(2). This court has jurisdiction over this appeal from the final
    decision of the district court disposing of all claims against all
    parties under 28 U.S.C. § 1291.

By treating the appeal as early rather than late, appellees re-
linquished the benefit of Rule 4(a)(7)(A)(ii).
    After the appellees filed their brief, this court alerted the
parties to a problem with the appeal’s timing. Once we did
so, appellees filed a supplemental jurisdictional statement
asserting that the appeal is late. And so it is—but because,
under Hamer, the benefit of Rule 4 may be waived or forfeit-
ed, appellees’ belated invocation of the Rule is unavailing.
Indrelunas shows that the appeal is jurisdictionally timely,
and no more is needed when the litigants do not notice other
problems until after the briefs have been filed.
    Enforcing waivers and forfeitures gives litigants incen-
tives to explore issues themselves rather than wait for the
court to do the work. It is best to have defects detected in
time to dismiss the appeal without the need for briefs and
argument. Because no one paid attention to Rule
4(a)(7)(A)(ii) until the briefs had been filed and argument
scheduled, it was too late to save time and effort; instead the
appellees’ belated invocation of Rule 4(a)(7)(A)(ii) just com-
plicated the appeal.
    This brings us to the merits. Police arrived at Katrina
Walker’s house with a warrant authorizing them to search
for heroin and “T,” a drug dealer. The warrant was support-
ed by information from “J. Doe,” a drug user whose source
was T (who Doe knew by sight and street name rather than
No. 17-2665                                                   5

full name). Doe told police that for the previous six months
she regularly bought heroin from T in the living room of a
house, which she knew by sight rather than street address.
She identified the house while driving with the police. Police
prepared an application for a search warrant and took Doe
with them when presenting the application to a state judge.
After placing Doe under oath, the judge asked her several
questions, believed Doe’s answers, and issued the warrant.
   Executing the warrant, officers found Walker but not T.
The house was a mess; one officer attested (without contra-
diction) that it had the appearance of a place from which
drugs were sold. Walker told the officers that she had a gun
but could not remember where it was. The search for this
gun, drugs, and evidence that T did (or didn’t) live in the
house took between 90 minutes and 2 hours. The officers left
without drugs or evidence of T’s whereabouts, and Walker
then filed this suit under 42 U.S.C. §1983. She contends that
the warrant was not supported by probable cause and that
the search was executed unreasonably because the officers
should have seen quickly that this was not T’s house.
   Walker’s goal in this litigation is to have a jury make a de
novo decision about whether the state judge should have is-
sued the warrant—that is to say, an independent decision
about probable cause, putting to one side the state judge’s
decision. But that’s not what federal law provides. Instead
the decision of the judge who issued the warrant receives
“great deference”. Illinois v. Gates, 

, 236 (1983);
United States v. McIntire, 

, 577–79 (7th Cir. 2008).
With the benefit of “great deference” the state judge’s prob-
able-cause evaluation must prevail.
6                                                   No. 17-2665

    According to Walker the state judge was not entitled to
rely on Doe, a first-time informant whose information had
not been corroborated by the police. Walker proceeds as if
Doe were an anonymous tipster, and, if she had been, then
corroboration would have been essential. Florida v. J.L., 

(2000). But Doe was not anonymous; we use a
pseudonym to protect her from retaliation, not because her
identity was unknown to the police. They knew her name
and background (she had an arrest record but not a convic-
tion); they met with Doe and her father, and Doe said that
she wanted to break her drug habit, a good reason for turn-
ing in her supplier. Doe testified in person before the judge
who issued the warrant and by doing this exposed herself to
as much as three years in prison if she was lying. 720 ILCS
5/26-1; 730 ILCS 5/5-4.5-45. The reports of known, accounta-
ble persons who claim to be victims of or participants in
crime (Doe was both) may establish probable cause without
corroboration; the police may leave to the judicial process
the sorting of truth from fiction. See, e.g., Gramenos v. Jewel
Companies, Inc., 

, 437–40 (7th Cir. 1986); Jenkins v.
Keating, 

, 585 (7th Cir. 1998); McBride v. Grice,

, 707 (7th Cir. 2009); Matthews v. East St. Louis,

, 706–07 (7th Cir. 2012). The state judge could
have told the police that they needed to do more investiga-
tion; by issuing the warrant instead, the judge entitled the
police to search without the risk of personal liability.
    Walker faults the warrant-application process for with-
holding from the state judge the lack of corroboration. Yet
neither Doe nor the officer who signed the application for
the warrant stated that Doe’s information had been corrobo-
rated; a reasonable judicial officer thus would have inferred
that it had not been. Nothing was concealed from the
No. 17-2665                                               7

judge—nor does it matter exactly when Doe pointed to the
house in which, she said, she had bought heroin (another
topic on which Walker faults the affidavit seeking the war-
rant).
    As for Walker’s contention that the police should have
left the house as soon as they discovered T’s absence: What
sense would that make? Drug dealers do not stay in their
distribution points 24 hours a day. The police arrived at a
disordered house that looked like a drug-distribution point.
Walker admitted having a gun. It took a while for the offic-
ers to sort through the debris, locate the gun, search for
drugs, and determine whether T lived in or used the house.
It cannot be called unreasonable to take two hours to ac-
complish these things.
                                                  AFFIRMED