Suella King died of strangulation in the early morning of February 27, 1980. Her body was found, sexually assaulted and half naked, near tennis courts behind an apartment building at 2135 Suitland Terrace, S.E. An indictment charged appellee, Willie L. Minick, with felony murder, D.C.Code 1973, § 22-2401, and rape, id, § 22-2801.
Appellee sought to suppress certain physical evidence, taken from his home and his person, as fruits of an unlawful, warrant-less entry and arrest. Appellee also moved to suppress an oral statement, made at his home at the time of arrest, as well as an exculpatory written statement, given an hour later at the police station. The trial court ordered suppression of the physical evidence and the oral statement, but denied the motion as to the written statement. The government appealed. D.C.Code 1973, § 23-104(a)(1). A divided panel of this court affirmed the trial court’s ruling. The full court voted to vacate the panel’s opinion and rehear the case en banc.
We conclude that there were “exigent circumstances” obviating the need for a warrant, and that the evidence, accordingly, should not have been suppressed. We reverse the trial court’s order and remand the case for further proceedings.
I.
Detective Earl C. Bryant, the sole witness at the suppression hearing, testified substantially as follows:
The police received a phone call from a security guard, Mr. Phillips, at approximately 12:35 a.m. on February 27, 1980. Phillips reported seeing a man dragging a woman into the woods behind an apartment building at 2135 Suitland Terrace, S.E. He described the man as wearing a white skull cap and a short, brown coat. Two police officers arrived at the scene, spoke with Phillips, and began searching the grounds. Phillips yelled to one of the officers that a man was leaving the area by the tennis courts. The police unsuccessfully chased the man, who was wearing a white skull cap and a brown jacket. Shortly thereafter, Ms. King’s body was discovered.
Detective Bryant, who was working at the homicide branch, received a phone call at 1:00 a.m. reporting the apparent homicide. He and his partner, Detective Brooks, arrived at the scene by 1:20 a.m. There, Detective Bryant observed that the woman’s clothing had been removed from the lower half of her body. In the dirt between her legs he saw knee impressions and, further back, shoe marks. The medical examiner at the scene concluded that the woman had been strangled and sexually assaulted.
Sometime between 1:20 and 2:00 a.m., the police found a wallet alongside one of the tennis courts. The wallet lay along the path where the man in the white skull cap and brown jacket had fled from the police, about twenty-five feet from the victim. The evidence technician opened the wallet at approximately 2:00 a.m.; inside, the driver’s license showed Willie Minick’s name and address, which was five blocks away.
The detectives continued their investigation at the scene until 4:00 a.m., when they returned to the homicide office to cheek for records of Willie Minick. At 4:30 a.m., Detective Brooks learned that Minick had previous arrests and one conviction for rape. One of the rapes for which he had been *876arrested, but not convicted, had taken place behind 2135 Suitland Terrace. Moreover, the description in the police file matched the one Phillips had given. At that point, the police decided to arrest Minick. They discussed the possibility of obtaining a warrant but rejected the idea, fearing that while they were getting the warrant “dirt, clothing, any exchange of hairs, or anything that would show contact with the victim ... would go down the drain with a shower or a bath.” Detective Bryant testified that, in his experience, at that time of night it would take at least two or three hours to get a warrant.
The police arrived at Minick’s home at 4:50 a.m. and knocked on the door. Min-ick’s sister opened it part way. Seeing the police, she stepped back; the officers could see a man, later identified as Minick, sitting in an armchair. One of the officers handcuffed Minick and advised him of his Miranda rights.1 The police seized a stained white smock from atop an ironing board visible from the armchair. They also seized a short brown coat lying next to the chair, identified by one of the officers as similar to the coat worn by the man who had run past the tennis courts shortly after the crime. They took Minick to the homicide office, where an officer photographed his clothes, beard, hair, and knees. Police also took clippings and combings from Minick’s head and pubic area. Twigs and debris were lodged in his ear and hair, and dirt covered his knees.
II.
The Fourth Amendment bars police from making a warrantless, noneonsen-sual entry for purposes of a routine felony arrest. Payton v. New York, 445 U.S. 573, 100 S.Ct. 1371, 63 L.Ed.2d 639 (1980). Citing Dorman v. United States, 140 U.S.App.D.C. 813, 435 F.2d 385 (1970) (en banc), the government proffers an exception, arguing that “exigent circumstances” justified the warrantless entry here. The United States Court of Appeals for the District of Columbia Circuit, in United States v. Lindsay, 165 U.S.App.D.C. 105, 110, 506 F.2d 166, 171 (1974), summarized the Dorman criteria for the trial court to consider in determining whether there are exigent circumstances:
(1) That a grave offense is involved, particularly a crime of violence;
(2) the suspect is reasonably believed to be armed;
(3) a clear showing of probable cause;
(4) a strong reason to believe that the suspect is in the dwelling;
(5) the likelihood of escape if not swiftly apprehended;
(6) a peaceful entry as opposed to a “breaking”; and
(7) the time of entry (night or day).
We are bound to accept the trial court’s finding, absent clear error. Brooks v. United States, D.C.App., 367 A.2d 1297, 1302 (1976).
Analytically, the court must address four questions: (1) At what time did the police decide they had sufficient cause to pursue Minick? (2) Did the police act reasonably in waiting that long to do so? (3) By the time the police were ready to move against Min-ick, were there exigent circumstances justifying a warrantless entry under Dorman, supra ? (4) If so, did the police enter the premises without unreasonable delay?
III.
The crime occurred at approximately 12:35 a.m. Sometime between 1:20 and 2:00 a.m., the police found a wallet twenty-five feet from the victim’s body with a driver’s license showing Minick’s name and address (five blocks away). A few hours later, at approximately 4:30 a.m., the police discovered additional, crucial evidence: Minick had a prior rape conviction and previous arrests for rape, including an incident at the very location where the deceased’s body had been discovered. Furthermore, Minick’s description in the police file matched witness Phillips’ description of the *877man leaving the scene. At that point, the police were satisfied that Minick probably had committed the crime.
IV.
If the police had probable cause to seek a warrant at 2:00 a.m., can they be faulted for declining to proceed that soon? See United States v. Rosselli, 506 F.2d 627, 630 (7th Cir.1974) (court evaluates claim of exigent circumstances from the time the police first “had a right to obtain a warrant”). Or, did the police use reasonable judgment in seeking more conclusive evidence than a lost wallet before deciding, at 4:30 a.m., to move against their prime suspect? See United States v. Gardner, 553 F.2d 946, 948 (5th Cir.1977) (“the reasonableness of a search under exigent circumstances is not foreclosed by the failure to obtain a warrant at the earliest practicable moment”), cert. denied, 434 U.S. 1011, 98 S.Ct. 722, 54 L.Ed.2d 753 (1978); United States v. McEachin, 216 U.S.App.D.C. 320, 326, 670 F.2d 1139, 1145 (1981) (same); United States v. Ferrara, 539 F.2d 799, 802 (1st Cir.1976) (same); Commonwealth v. Forde, 367 Mass. 798, 802, 329 N.E.2d 717, 720 (1975) (same); cf. Cardwell v. Lewis, 417 U.S. 583, 595, 94 S.Ct. 2464, 2472, 41 L.Ed.2d 325 (1974) (applying the same rule in the context of a car search: “[W]e know of no case or principle that suggests that the right to search on probable cause and the reasonableness of seizing a car under exigent circumstances are foreclosed if a warrant was not obtained at the first practicable moment”).
The answer here may be crucial. Suppose that the court evaluates a claim of exigent circumstances from the time the police first had probable cause to obtain a warrant. If the police elect not to seek a warrant but instead to continue their investigation, their right to make a warrantless entry, after finding more evidence that “clinches” the case, may have evaporated because a court could find they had time, since the advent of probable cause, to obtain a warrant. Alternatively, assume that the police are not obliged to seek a warrant until, in their reasonable judgment, they are ready to do so based on evidence beyond that required to establish mere probable cause. A claim of exigent circumstances will be available at the time the police are ready to move, for they will not have been expected to seek a warrant on less conclusive evidence. In short, the court’s decision about the point in time from which the police should be expected to seek a warrant may be critical in determining whether the police acted with sufficient dispatch to claim exigent circumstances, and thus may determine the extent that the police will investigate before pursuing possible subjects.
We conclude that the court should start the count for a warrant as of the time the police reasonably conclude they should move against a suspect, even though by that time they may have more than minimum probable cause for the entry. We reach this conclusion for two reasons. First, an approach requiring strict timing of the inquiry from the advent of probable cause is unrealistic; it would require the court to apply “20-20 hindsight” to a fluid situation which, as it develops, is typically a difficult judgment call. United States v. Campbell, 581 F.2d 22, 27 (2d Cir.1978). Second, an approach that forces the police to seek a warrant as soon as they arguably have probable cause may result in premature police intrusions upon individual privacy — intrusions which may not occur if the police investigate further. See United States v. Whitfield, 203 U.S.App.D.C. 102, 108, 629 F.2d 136, 142 (1980), cert. denied, 449 U.S. 1086, 101 S.Ct. 875, 66 L.Ed.2d 812 (1981); Campbell, supra at 27. In this case, for example, a wallet lost in a tennis court area is thin evidence to support an uninvited police entry into someone’s home. We recognize that the police may obtain a warrant but not execute it until they have more evidence; but given that obtaining a warrant requires an investment of time and possible diversion from the investigation, it seems unlikely that forbearance would be the norm once a warrant was in hand.
*878In this case, we conclude that the police acted reasonably in waiting until 4:30 a.m. to proceed against Minick.2 The warrant clock did not begin to run earlier. See Gardner, supra at 948; Ferrara, supra at 802; Forde, supra 367 Mass. at 802, 329 N.E.2d at 720.3
V.
The next — and central — question is whether, at 4:30 a.m., there were exigent circumstances justifying a warrantless entry.
A. Five of the seven Dorman criteria are easily disposed of here. Although there is no record basis for a conclusion that the “suspect [was] reasonably believed to be armed,” id. 140 U.S.App.D.C. at 320, 435 F.2d at 392, the offense obviously was a grave one, there was strong reason to believe that Minick was at home,4 and the peacefulness of the entry offset concern that the police entered at night.5
This leaves the other two criteria, which are determinative here: (1) “a clear showing of probable cause ... to believe that the suspect committed the crime,” i.e., a showing greater than “merely the minimum of probable cause” required for a warrant, id. 140 U.S.App.D.C. at 320-21, 435 F.2d at 392-93; and (2) “a likelihood that the suspect will escape if not swiftly apprehended.” Id. at 321, 435 F.2d at 393. Of particular relevance is this court’s expansive view of the latter, escape criterion: “Under limited circumstances, the ‘likelihood of escape’ inquiry properly includes consideration of the probability that evidence as well as the suspect may be lost.” Brooks, supra at 1303 (footnote omitted); see Thomas v. United States, D.C.App., 352 A.2d 390, 391 (1976).
The police officers testified that once they had sufficient cause to pursue Minick they did not seek a warrant because, in their experience, it had taken two or three hours at that time of the morning, and they feared losing evidence such as “dirt, clothing, ... exchange of hairs, or anything that would show contact with the victim.”
The trial court analyzed the police explanation as follows:
It is a very close question on the probable cause. Undoubtedly they had proba*879ble cause for the issuance of a warrant, but whether they had reasonably trustworthy information to believe that the suspect committed the crime, over and beyond the minimum requirements of probable cause, is doubtful.
They had strong reason to believe the suspect was on the premises. They had— they may have suspected that he might escape if not swiftly apprehended, but there are no facts to support that conclusion. It was not developed at the hearing as to how long or short a period of time he lived at the address, or if the police knew that at the time, or any of the attendant facts. There is no evidence that the identification of the Defendant was found in a truly incriminating place, or that they must have assumed it was found there.
Assuming these things to be so, the police were very candid in admitting that their purpose in going at that time without getting a warrant was twofold — one, that in prior experience, at that time of morning, the earliest they have been able to get a warrant is two or three hours. I’m not sure that it was an inconvenience, or they felt that interfered with ordinary police work.
They also went because they discovered what appeared to be knee marks in the dirt between the legs of the decedent, and they wanted to get to the Defendant before he had a chance to remove the dirt by bathing or whatever. They discovered these facts some time after 1:30 and before two o’clock in the morning.
Taking — using their time frame, had they immediately applied for a warrant, they had reasonable expectations that they would have it by five o’clock. They made no effort whatsoever to obtain a warrant, but, instead, at five o’clock, they decided that the circumstances required their going without a warrant. There was no reason to believe that if the Defendant, or the suspect was going to bathe, that he had not bathed by five o’clock in the morning. It’s no more persuasive than if they had decided they were going in January rather than April be cause there was a greater possibility that the sooner you go, the better; but, beyond some rather generalized reasoning, there was no reason to believe that.
So, the Court does not have to address itself as to whether or not the police would have a right to make a warrantless entry for the purpose of seizing evidence, when there was no realistic exigent circumstances for preserving or believing it had been preserved by the time they went in. The right of entry of a private dwelling is a sacred trust that should not be invaded except upon exceptions to the warrant requirement.
B. As to probable cause, the trial court’s analysis is inconclusive. The court appears to say the police “had probable cause for the issuance of a warrant” at 2:00 a.m. and should have “immediately applied for a warrant” at that time. But the court also suggests that three hours later, at the time of entry, “whether they had reasonably trustworthy information to believe that the suspect committed the crime, over and beyond the minimum requirements of probable cause, is doubtful.” Both analyses cannot be correct. If there was probable cause for a warrant at 2:00 a.m. based on the discovery of the wallet and Minick’s driver’s license, there obviously was a showing of probable cause beyond the “minimum” at 4:30 a.m. when the police discovered the prior conviction, arrests, and identification evidence. If, on the other hand, there was only “minimum” probable cause at 5:00 a.m. to believe Minick had committed the crime, there could not have been probable cause for a warrant at 2:00 a.m., before the police had discovered the substantial, additional evidence.
As we see it, therefore, the court did not make a discernible probable cause finding. This court accordingly must make its own evaluation of whether, at the time of entry, there was a “clear showing of probable cause” (i.ewell beyond the “minimum”) to believe that Minick had committed the crime. Dorman, supra 140 U.S.App.D.C. at *880320-21, 435 F.2d at 392-93.6 We are satisfied that there was.
C. As to the final factor, possible loss of evidence, the trial court found that no exigency remained at 5:00 a.m., when the police entered Minick’s apartment. The court stated, “There was no reason to believe that if the Defendant, or the suspect was going to bathe, that he had not bathed by five o’clock in the morning.” Perhaps as a result of finding no exigency, the court curtailed its inquiry and thus dealt only with evanescent evidence; it did not specifically address the police concern about the suspect’s clothing.
In making its finding, the court presumably applied the following test: whether at 5:00 a.m. the police officers reasonably concluded there was a substantial likelihood that critical evidence was still on the premises and would be lost, absent immediate entry. See Brooks, supra at 1303 n. 3.
When we focus on the evanescent evidence involved — dirt, hair, and other debris — it seems fair to accept the trial court’s premise that this evidence can be washed off the body easily. The government, after all, did not argue that traces of such evidence will remain undisturbed for several hours, despite an effort to clean the body.7 As to the clothing, there is no serious impediment to its disposal.8 Thus, the question is this: did the trial court clearly err in finding, in effect,, that reasonable police officers, at 5:00 a.m., would have to conclude that if Minick were ever going to do so, he assuredly had washed all the loose evidence off his body and disposed of his tell-tale clothing within 4V2 hours of the crime?
As noted earlier, this court’s review of the trial court’s findings as to exigent circumstances is limited to reversal only for clear error. Brooks, supra at 1302. But the trial court made no finding (except an implicit one) about Minick’s clothing, which was as important to the police as the dirt, hair, and other debris on the suspect’s flesh. Moreover, in finding “[tjhere was no reason to believe” that the suspect “had not bathed by 5 o’clock in the morning” (if he were going to bathe at all), the court necessarily was speculating about what any — and every — criminal was likely to do once he knew the police were after a suspect.9 The court was not basing this finding, or its implied finding that the clothing had been disposed of, on evidence related to Minick himself, such as evidence tending to prove he knew the police were after him, see note 9 supra, testimony about his behavior pattern, or questions of witness credibility. No facts, in other words, were in dispute. Under these circumstances, therefore, the court’s “finding” as to the loss of evidence was actually in the nature of a legal conclusion: there could not have been exigent circumstances at the time of entry because every criminal, knowing the police are searching for an assailant, will wash all incriminating dirt, hair, and debris off his body, and dispose of all clothing used during the assault, within 414 hours of the crime (if he ever is going to do so). See Robinson, supra 174 U.S.App.D.C. at 353, 533 F.2d at 580.
We cannot endorse the trial court’s analysis. To call it a finding of fact would mischaracterize what the trial court was doing. Basically, the court made a univer*881sal pronouncement about human behavior— in our parlance, a conclusion of law — which the appellate court has a responsibility to review, not only for its application to the case at hand but also for the norm it establishes for the future. The trial court’s approach is too inflexible for this jurisdiction to adopt.
“The exigent circumstances doctrine is to be applied to the facts as perceived by the police at the time of entry....” Brooks, supra at 1302. We do not believe reasonable police officers had to assume either that their suspect would have acted so rationally and thoroughly that he eliminated all incriminating evanescent evidence and clothing within 4V2 hours of the crime or that he never would do so. See Dorman, supra 140 U.S.App.D.C. at 321, 435 F.2d at 393.10 To the contrary, we conclude that the police officers acted reasonably in believing that critical evidence was still likely to be on the premises within £k hours of the crime, but that every passing moment jeopardized that possibility.11
Accordingly, we conclude that, given our standard of review and considering all the Dorman factors, a warrantless entry was justified at 4:30 a.m.
VI.
There is the question, finally, whether the police — confronted by exigent circumstances at 4:30 a.m. — entered the premises without unreasonable delay.12 Even when the Dorman criteria are met, the court shall not excuse the unexplained failure of the police to procure a warrant if they unreasonably delayed their investigation or entry. See United States v. Chuke, 554 F.2d 260, 263 (6th Cir.1977). “The essence of exigent circumstances is the lack of time to obtain a warrant without thwarting the arrest or making it more dangerous. Where time was adequate, failure to obtain a warrant should not be excused.” Latzer, Enforcement Workshop: Police Entries to Arrest—Payton v. New York, 17 Crim.L. Bull, 156, 165 (1981).
There is no indication that the police deliberately stalled or unreasonably delayed their investigation to avoid the necessity of obtaining a warrant. See note 2 supra. From the time they learned of the crime until the time they decided (at 4:30 a.m.) to make the arrest, the police continually were engaged in accumulating evidence.
Nor did the police unreasonably delay their entry. They entered the apartment and arrested Minick at 4:50 a.m.,13 only 20 minutes after concluding they had sufficient cause to do so. There is simply no room for an argument that the police moved too slowly to justify a warrantless entry; no one has suggested that the police could have obtained a warrant in 20 minutes.14 Compare Niro v. United States, 388 *882F.2d 535, 536, 539-40 (1st Cir.1968) (war-rantless entry unlawful where officers delayed more than 12 hours between time they stopped accumulating evidence and seizure); Forde, supra 367 Mass. at 801-02, 329 N.E.2d at 719-20 (same; three-hour delay); State v. Dunlap, 395 A.2d 821, 823-25 (Me.1979) (same; 15½ hour delay); State v. Beede, 119 N.H. 620, 629, 406 A.2d 125, 131 (1979) (same; one-day delay), cert. denied, 445 U.S. 967, 100 S.Ct. 1659, 64 L.Ed.2d 244 (1980).
VII.
In summary, the police conducted their investigation without delay and reasonably concluded they had clear probable cause to pursue Minick at 4:30 a.m. They confronted exigent circumstances justifying a war-rantless entry of his home at that time. They did not unreasonably delay; they entered with dispatch at 4:50 a.m., 20 minutes after determining they had sufficient cause to do so. They could not reasonably have been expected to obtain a warrant during this very short interval. At every critical decisional juncture, therefore, the police acted properly.
Reversed and remanded for further proceedings.
. Miranda v. Arizona, 384 U.S. 436, 86 S.Ct. 1602, 16 L.Ed.2d 694 (1966).
. There is no indication that the police deliberately were stalling to avoid the necessity of obtaining a warrant. Compare United States v. Jones, 635 F.2d 1357, 1361-62 (8th Cir.1980) with United States v. Houle, 603 F.2d 1297, 1300 (8th Cir.1979).
. The significance of the foregoing analysis would be diminished, if not eliminated, were it possible under our local rules to obtain warrants “based on sworn oral testimony communicated by telephone,” United States v. Robinson, 174 U.S.App.D.C. 351, 358, 533 F.2d 578, 585 (1976) (en banc). Such expeditious availability of a warrant presumably would cut down on the need to invoke the exigent circumstances exception in many cases. See McEachin, supra 216 U.S.App.D.C. at 327-29, 670 F.2d at 1146-48. Fed.R.Crim.P. 41(c)(2) (warrant upon oral testimony) now authorizes a warrant sought by telephone, but our Super.Ct.Cr.R. 41 does not.
. The trial court found that a grave offense was involved. The trial court also found that the police “had strong reason to believe the suspect was on the premises.” Although a witness saw a man fleeing from the scene of the crime in a direction different from the direct route to Minick’s home, the fact that he lived only five blocks away and the fact that the incident occurred in the early morning hours combine to give a strong reason for believing he would be at home. See Dorman v. United States, 140 U.S.App.D.C. 313, 321, 435 F.2d 385, 393 (1970) (en banc). But see Fisher v. Volz, 496 F.2d 333, 338 (3d Cir.1974) (requiring “probable cause” to believe that the suspect is in the dwelling, defined as more than “strong reason” to believe so).
.The “time of entry” factor cuts both ways. Nighttime entry generally involves a greater intrusion on Fourth Amendment rights, but the delay in obtaining a nighttime warrant might underscore the level of urgency in effectuating a warrantless arrest. See Dorman, supra 140 U.S.App.D.C. at 321, 435 F.2d at 393. The trial court did not make a definite finding with respect to which way the time of entry would cut in this particular case. The court’s only reference to this factor came when defense counsel argued that nighttime entry, as in this case, results in a greater intrusion. The trial court then noted that, on the other hand, “at nighttime [appellee] would be more likely to be home.”
. Appellate deference to the trial court is limited in this context to findings of fact. See Brooks v. United States, D.C.App., 367 A.2d 1297, 1302 (1976).
. An argument that traces of tell-tale evidence are likely to remain after a scrubbing could prove too much. Whatever traces cannot easily be washed off are likely to remain until a warrant is available.
. It is likely to be more difficult to dispose of clothing than the other evidence, however, for it may require a trip out of the apartment if not out of the building.
.The record reflects that soon after the crime the police unsuccessfully chased a suspect identified as the man who took a woman into the woods. Although Minick, therefore, may have been running from the police, there is no evidence that he knew his wallet was missing or that he would have reason to believe the police, who never caught up with him, had a clue to his identity.
. In Dorman, supra, the court said that after four hours “[t]he police were still dealing with a relatively recent crime, and prompt arrest might locate and recover the instrumentalities and fruits of the crime before otherwise disposed of.” Id. 140 U.S.App.D.C. at 321, 435 F.2d at 393.
.The fact that it is speculative whether a criminal suspect would destroy all evanescent and other incriminating evidence during the first 4‘A hours after the crime does not diminish the urgency of pursuing such evidence as quickly as possible. We agree with the trial court that there will come a point where one would have to say that the police waited too long after the crime, in contrast with waiting too long after a finding of probable cause, to claim exigent circumstances in lieu of obtaining a warrant. In the present case, we have not reached that point.
. Akin to this inquiry is the question whether the police could have prevented the exigency. See United States v. Rosselli, 506 F.2d 627, 630 (7th Cir.1974). Here, the police could not have done so, for even if they had placed a guard at Minick’s door, they could not have prevented destruction of evidence. See Brooks, supra at 1303.
. The dissent, reflecting the trial court, refers to entry “[a]t 5:00 a.m.” At 882. However, according to the only evidence of record, Officer Bryant’s testimony, the police arrived at approximately 4:50 a.m.
. Given that it was reasonable for the police not to move against Minick until 4:30 a.m. and *882that they did so thereafter within 20 minutes, we need not consider the reasonableness of the officers’ undocumented assertion that it would take two or three hours to get a warrant.