Juliet C. Gaddy was convicted of narcotics possession after police arrested her for driving with a suspended license and discovered cocaine in a search incident to arrest. Because her license status information from the Department of Licensing (DOL) was reasonably reliable, we hold that the officers had probable cause to arrest.
I
Juliet Gaddy was stopped by a police officer after she failed to signal a right-hand turn of her automobile. When she was unable to produce a driver’s license, the officer asked for her name and birth date so that he could verify her driver’s status on the mobile data terminal located in his police cruiser. She complied.
The officer learned that Gaddy’s license was suspended. He and his partner returned to her vehicle and arrested her for driving with a suspended license. In a search of her vehicle incident to arrest, the officers discovered a substance they suspected was cocaine. Their suspicions proved correct and she was convicted of possession of cocaine. Gaddy appeals.
II
Gaddy first argues that her conviction must be reversed because the trial court failed to enter written findings of fact on her motion to suppress evidence until after *705she filed her opening brief on appeal. CrR 3.6(b) requires that at the conclusion of a hearing on a motion to suppress, the trial court shall enter written findings of fact and conclusions of law. But we will not reverse a conviction for tardy entry of findings unless the defendant can establish either that she was prejudiced by the delay or that the findings and conclusions were tailored to meet the issues presented in her appellate brief.1
Gaddy argues that the lack of findings prejudiced her because the court’s oral decision failed to resolve whether her driver’s license was actually suspended at the time of the stop. But this is a substantive claim of error. It does not demonstrate prejudice as a result of delayed entry of findings. And there is no evidence that the findings were tailored to the issues she raises on appeal. Reversal is not required.
Gaddy next argues that the officer did not have probable cause to arrest her for driving with a suspended license. She contends that the license status information the police received on their mobile data terminals from the DOL was not reliable. Although Gaddy did not raise this issue to the trial court, because the issue implicates her constitutional right of privacy under the Fourth Amendment and article I, section 7 of the Washington Constitution, we will resolve it.2
Subject to narrow exceptions, an officer’s warrant-less seizure of a person is per se unreasonable.3 But police may arrest a person without a warrant if they have probable cause to believe that she is driving with a suspended license.4 Probable cause exists if there are sufficient facts and circumstances on reasonably trustworthy information that would cause a person of reasonable caution to believe *706that an offense has been committed.5 Only the probability of criminal activity is required to show probable cause, not a prima facie showing of it.6
A determination of probable cause is made on the officer’s knowledge at the time of the arrest.7 Because the facts supporting probable cause are often founded on hearsay and hastily garnered knowledge, it is sufficient if the information is reasonably trustworthy; it need not be absolutely accurate.8 Where police have made a warrantless arrest, the State bears the burden of proving the reliability of the information that formed the basis of probable cause.9 Information obtained after the arrest may not be used to retroactively justify it.10
Under the “fellow officer” rule, an officer may rely on information contained in a police bulletin or “hot sheet” in effecting an arrest.11 But if the issuing agency does not have sufficient information to constitute probable cause, the arrest is illegal, regardless of the good faith of the arresting officer.12 Thus, it is not the hot sheet itself that supports probable cause, but the reliability of the original source of the information in the hot sheet.
In State v. Manee, Division Two of this court held that police did not have probable cause to arrest the driver of an auto that a police bulletin indicated was stolen. The court *707noted that probable cause initially existed because the victim had reported the auto stolen.13 A citizen informant, as opposed to a “professional” police informant or an anonymous tipster, is presumptively reliable.14 But the victim later canceled the report and, although the police department had a record of taking the call, at the time of the arrest it had not yet updated its bulletin.15 The court held that because the police failed to offer any evidence that the delay in updating its records was reasonable, probable cause did not exist to arrest the driver.16 It was not the error in the report that was dispositive, but only that the police had not demonstrated that their record keeping was reasonably reliable.17
Here, the legislature, through a comprehensive statutory scheme, has vested in the DOL the responsibility of administering all aspects of motor vehicle driver licensing.18 Moreover, in State v. Monson,19 our Supreme Court stated that:
“The special trustworthiness of official written statements [from the DOL] is found in the declarant’s official duty and the high probability that the duty to make an accurate report has been performed.”[20]
*708We hold that the information police officers receive on their mobile data terminals from the DOL is presumptively reliable.
Gaddy argues that she nevertheless rebutted the presumption of reliability by producing a report from the DOL evidencing that her license was issued two weeks prior to the date she was arrested. In Manee, the court held that the defendant had demonstrated the unreliability of police information by showing both that the stolen vehicle report was erroneous and that the police department had notice of it.21 But in State v. Perea,22 the court rejected a defendant’s claim that DOL information was not reliable because it was a week old and it is possible for drivers licenses to be reinstated within a week.23 He did not show that his license was, in fact, reinstated. Under the commonsense test for “staleness,” the court held that the information was sufficiently reliable to support probable cause.24
In this case, Gaddy did not produce evidence that her license was actually valid on the day of her arrest. Absent a showing that the information on which the police relied was in fact erroneous, Gaddy has failed to rebut the presumption that the DOL report was reasonably reliable. The officer had probable cause to arrest Gaddy.
We note that the officer’s basis for probable cause included not only the license suspension report, but also the fact that Gaddy could not produce a driver’s license prior to her arrest and that her demeanor was uncooperative and flighty during the encounter. Taken collectively, substantial evidence supported the trial court’s conclusion that probable cause existed for Gaddy’s arrest.25
*709We decline to consider Gaddy’s pro se supplemental brief because she cites neither to authority nor to the record, and provides no analysis.26
Affirmed.
Kennedy, J., concurs.
State v. Byrd, 83 Wn. App. 509, 512, 922 P.2d 168 (1996).
RAP 2.5(a).
State v. Hastings, 119 Wn.2d 229, 234, 830 P.2d 658 (1992).
RCW 10.31.100(3)(e).
State v. Graham, 130 Wn.2d 711, 724, 927 P.2d 227 (1996).
State v. Seagull, 95 Wn.2d 898, 906-07, 632 P.2d 44 (1981).
State v. Mance, 82 Wn. App. 539, 541, 918 P.2d 527 (1996).
See State v. Reeb, 63 Wn. App. 678, 681-82, 821 P.2d 84 (1992) (information provided by DOL need only be reasonably trustworthy, not absolutely accurate, to support adequate cause); Franks v. Delaware, 438 U.S. 154, 165, 98 S. Ct. 2674, 57 L. Ed. 2d 667 (1978) (defendant may challenge warrant only on showing that police officer made deliberate false assertions in affidavit supporting probable cause).
State v. Sandholm, 96 Wn. App. 846, 848, 980 P.2d 1292 (1999).
Mance, 82 Wn. App. at 542.
Whiteley v. Warden, Wyo. State Penitentiary, 401 U.S. 560, 568, 91 S. Ct. 1031, 28 L. Ed. 2d 306 (1971); Mance, 82 Wn. App. at 542.
Whiteley, 401 U.S. at 568.
State v. Mance, 82 Wn. App. 539, 542, 918 P.2d 527 (1996).
State v. Wakeley, 29 Wn. App. 238, 241, 628 P.2d 835 (1981).
Mance, 82 Wn. App. at 543-44.
Mance, 82 Wn. App. at 545.
Manee is not on point, despite the dissent’s reliance upon it. There, the party challenging the presumptively rehable police bulletin proved that it was false, and that the police were at fault for failing to timely correct their record keeping. No similar showing has been made in this case. The DOL is at least as presumptively reliable as a citizen informant. It was Gaddy’s burden to rebut that presumption. She failed to obtain a finding in her favor on that issue.
ROW 46.01.040.
113 Wn.2d 833, 784 P.2d 485 (1989).
Monson, 113 Wn.2d at 845 (quoting Edward W. Cleary, McCormick on Evidence § 315, at 889 (3d ed. 1984) (sworn records from DOL are admissible hearsay evidence)).
Mance, 82 Wn. App. at 542.
85 Wn. App. 339, 932 P.2d 1258 (1997).
Perea, 85 Wn. App. at 343.
Perea, 85 Wn. App. at 343.
See Sandholm, 96 Wn. App. at 848 (although police buletin of stolen vehicle was not reliable, probable cause nevertheless existed for arrest because the report, in combination with the defendant’s nervous demeanor and the physical condition *709of the auto which indicated that it had been stolen, was sufficient data to constitute probable cause).
RAP 10.3,10.4; State v. Camarillo, 54 Wn. App. 821, 829, 776 P.2d 176 (1989) (court will not review issues raised in pro se brief that contains no references to the record); State v. Berrysmith, 87 Wn. App. 268, 279, 944 P.2d 397 (1997), review denied, 134 Wn.2d 1008 (1998) (appellate court need not reach pro se argument that is unsupported by authority); State v. Marintorres, 93 Wn. App. 442, 452, 969 P.2d 501 (1999) (conelusory pro se supplemental brief that identified no specific legal issues not considered).