Thomas J. Brunson appeals convictions for his part in the armed robbery of the Gotha, Florida post office and the murder of its postmistress.1 He argues that the district court erred by (1) refusing to suppress a statement and fingerprints taken from him by postal inspectors; (2) admitting evidence of his participation in another armed robbery committed four days before the post office robbery; and (3) refusing to direct a verdict of acquittal. We affirm.

I. FACTS.

A little before 3:30 p. m. on July 21, 1975 Marion Bush, a resident of the small rural community of Gotha, was watching television at home when she heard a loud noise from the vicinity of the nearby post office. She looked out her window and saw two black men emerge from the post office and drive off in a light colored Cadillac. She rushed to the post office and found that the postmistress, Marion Loraine Smith, had been shot to death.

Bush telephoned the Orange County sheriff's office, which sent deputies to secure the post office. United States postal inspectors and sheriff's deputies immediately began an intensive investigation. Although no one had witnessed the killing, a number of Gotha residents reported seeing a car and men matching those described by Bush driving around Gotha on the day of the killing. Two people had seen one black man inside the post office and the Cadillac outside the post office minutes before the murder, but no one remembered the men's faces. A fingerprint expert lifted latent prints from the post office, and an audit revealed that $288.70 in cash was missing.

The first break in the case came at about 7:00 p. m. on July 30, when fingerprints lifted from the post office counter were found to match known prints of a Glen Herman. Investigators already had determined that a Glen Herman recently had bought a Cadillac similar to the one seen in Gotha on the 21st, and they now launched a concerted effort to find Herman, the Cadillac, and anyone who knew Herman.

During this effort the investigators came to believe that one of Herman's associates was an Aaron Brunson, whom the investigators believed also was called "Black Boy."2 Aaron Brunson was thought to live at a particular address in a poor neighborhood of Winter Garden, Florida, which is a few miles northwest of Gotha. At about 9:30 p. m. on the 30th four postal inspectors and a sheriff's deputy left the operational headquarters for the case, the 33rd Street Annex of the Orange County Sheriff's Department, and drove in two cars to the neighborhood where they believed Aaron Brunson lived. Their purpose, the investigators later testified, was to locate Aaron "Black Boy" Brunson for an interview as to Herman's whereabouts, to look for another, unnamed associate of Herman, and to keep an eye out for Herman's Cadillac. Record Vol. II at 206-07, 210, 241, 245-56, 253, 255-56, 271-72, 279, 294, 303-04. Five investigators went because of the possibility they might run across Herman himself, id. at 245, 364-65, and because the neighborhood was known to be a rough one, id. at 268-70, 277-78, 304, 366.

What transpired next formed the crux of the suppression issue and was explored in great detail at the pre-trial suppression hearing. Four of the five investigators who went to Winter Garden that night testified. They agreed that Postal Inspector Bowers and Deputy Mack, dressed in civilian clothes and driving an unmarked car, parked in front of the house where they thought Aaron Brunson lived. Bowers and Mack knocked on the front door, identified themselves to the person who answered, and said they would like to see "Black Boy" Brunson. The person who answered shouted up to the second floor of the house to "Black Boy." A man appeared on the second story porch and asked who wanted to see him. Mack shouted up that he was from the sheriff's office.

"Black Boy" came down the back stairs of the house and up a side alley to the front, where Bowers and Mack again identified themselves. They told "Black Boy" they would like to talk to him, and the three walked to Mack and Bowers' car. There they were joined by Postal Inspectors Broadwater, Post, and Miller, also in plain clothes, who had been waiting near the side or back of the house.

The investigators told Brunson that they would like to talk to him at their headquarters. Inspector Broadwater testified that he told Brunson, "I want you to do it voluntarily. You are not under arrest," and that Brunson replied, "Certainly." Record Vol. II at 238. The investigators also told Brunson that they would bring him home after his interview. Id. at 273-74. They asked whether Brunson would like to tell his family where he was going, and Deputy Mack told the family where Brunson was going and that the investigators would bring him home after his interview. Id. at 223, 273. The investigators described Brunson's attitude toward going with them as "most cooperative," id. at 224 (Inspector Bowers), "very cooperative," id. at 239 (Inspector Broadwater), 267 (Deputy Mack), and "completely cooperative," id. at 291 (Inspector Post).

The investigators also were unanimous in testifying that none of them told Brunson he was under arrest or so much as touched him, let alone frisked, searched, or handcuffed him. Id. at 223, 225, 238-39, 267-68, 273, 290-91, 292. Although the investigators were armed, their weapons were not visible. Id. at 248-49, 267, 291, 301. They made it clear at the hearing that they had no intent to arrest or detain Brunson, because at that time they knew no more than that Aaron or "Black Boy" Brunson knew Herman. Id. at 239, 242, 292.3 They also explained that they preferred to conduct the interview at their headquarters because a crowd was milling around the house, id. at 229, 236-38, because the house itself appeared to be crowded, id. at 229, and because they had pictures of Herman at headquarters, id. at 237. They stated that they would have interviewed Brunson at home if he had asked them to, id. at 300, and that if Brunson had asked to be let out of the car or taken home during the ride to headquarters, they would have complied, id. at 239, 293. During the investigation at least one other person had been interviewed at the operational headquarters rather than at his home or place of business. Id. at 215.

Brunson rode to the 33rd Street Annex with Broadwater, Post and Miller. On the way there Broadwater asked Brunson if his first name was Aaron and learned, for the first time, that "Black Boy" Brunson was not Aaron Brunson, but rather his brother Thomas Brunson. Id. at 240-41. Broadwater also made some "small talk," asking what Brunson did for a living and learning that he picked oranges, id. at 240, but no other questioning took place on the ride to the Annex.

At about 10:15 p. m. they arrived at the Annex and Brunson was shown into the office where the interview was to take place. Detective Nazarchuk and Postal Inspector Weaver came in and introduced themselves to Brunson. They told him they were investigating the Gotha murder and read him the Miranda rights, which Brunson said he understood.4 Brunson signed a card waiving his right to have an attorney present during the interview. Id. at 312-14.

After some preliminary confusion the officers determined that Brunson did know Glen Herman, but only by the name "Willie." Nazarchuk began questioning Brunson about his association with Herman. Brunson said that he had ridden with Herman in Herman's Cadillac on occasion. When Nazarchuk asked whether Brunson had ridden with Herman on July 21st, Brunson first gave inconsistent accounts of his activities that day. Under further questioning he said he wanted to tell the investigators the truth. Id. at 316, 334-35. They took a short break, id. at 318, 360-61, and Brunson then told the investigators that he had been with Herman inside the Gotha post office when Smith was killed, but that Herman was the one who killed her and that he, Brunson, had not known beforehand that Herman was going to rob the post office or kill the postmistress.5

After exploring the details of Brunson's story, the investigators asked whether he would allow them to tape record his version. He agreed, and at 12:20 a. m. the investigators started the recording machine, read Brunson his Miranda rights again, and again elicited the details from him.6 The officers then formally arrested Brunson for first degree murder and robbery of the post office and took his fingerprints. These prints later proved to match previously unidentified latent prints lifted from the counter of the Gotha post office. The investigators testified that at no time did either of them make any threats or promises to Brunson, id. at 311, 361-62, 368, and that he seemed willing to relate his story, id. at 314, 315, 321-22, 356.

Brunson himself also testified at the suppression hearing. His testimony, in the main, substantiated that of the investigating officers. Although he said he had thought he was under arrest at his home and that he did not know he did not have to go to the Annex with the officers, Record Vol. I at 164, Brunson admitted that they did not tell him he was under arrest, id. at 175, or frisk him, id. at 174-75, or handcuff him, id. at 175, or show weapons to him, id. at 174, 176, and that upon their request he had agreed to go with them, id. at 176. He also remembered telling Nazarchuk and Weaver that he understood the rights they had read him, id. at 183, although he claimed that he thought he could not have an attorney unless he paid for one, id. at 168.

After hearing all this evidence the district court in a written order denied Brunson's motion to suppress the tape-recorded statement and fingerprints taken on the night of the 30th. At trial the government relied primarily on the fingerprint evidence, a transcript of Brunson's statement, and evidence that four days before the Gotha murder Brunson and Herman had committed an armed robbery of a Magik Market in Winter Garden, which evidence is rehearsed in Part III infra. Brunson testified in his own behalf at trial, admitting the substance of his statement to investigators but again denying that he had any foreknowledge that Herman was going to rob the post office or kill Smith. The defense also attempted to establish an alibi for the night of the 17th, when the Magik Market was robbed. After hearing all the evidence the jury, which was sequestered throughout the trial, found Brunson guilty on both the murder and the armed robbery counts. The court sentenced him to consecutive prison terms of life and twenty-five years, and Brunson brings this appeal.

II. MOTION TO SUPPRESS.

In support of his contention that the district court should have granted his motion to suppress, Brunson argues that his initial encounter with investigators and his journey with them to the 33rd Street Annex constituted an arrest without probable cause, illegal under the Fourth Amendment,7 and that the illegal arrest "tainted" the subsequent taking of his statement and fingerprints.8 See Brown v. Illinois, 422 U.S. 590, 95 S. Ct. 2254, 45 L. Ed. 2d 416 (1975); Wong Sun v. United States, 371 U.S. 471, 83 S. Ct. 407, 9 L. Ed. 2d 441 (1963). The government, conceding that the investigators did not have probable cause to arrest Brunson, argues that he was not arrested at all, but rather voluntarily accompanied investigators to the 33rd Street Annex for the interview; and that in any event, the giving of Miranda warnings before questioning helped to purge any taint that might have occurred. As we read its order denying Brunson's motion to suppress, the district court found that Brunson "accompanied the officers voluntarily and not on account of coercion either physical or psychological; " hence, it thought that no arrest at all had been made, let alone an illegal one. Record Vol. I at 411.9 Although Brunson attacks this finding as "purely erroneous," Brief for Appellant at 17, 22,10 we uphold it.11

Terry v. Ohio, 392 U.S. 1, 88 S. Ct. 1868, 20 L. Ed. 2d 889 (1968) teaches that, under the Fourth Amendment, "whenever a police officer accosts an individual and restrains his freedom to walk away, he has 'seized' that person." Id. at 17, 88 S.Ct. at 1877; see also United States v. Brignoni-Ponce, 422 U.S. 873, 878, 95 S. Ct. 2574, 45 L. Ed. 2d 607 (1975); Davis v. Mississippi, 394 U.S. 721, 724-28, 89 S. Ct. 1394, 22 L. Ed. 2d 676 (1969).12 The detention of a person need not be accompanied by formal words of arrest or stationhouse booking in order to constitute an "arrest" requiring probable cause under the Fourth Amendment. Davis v. Mississippi,supra, 394 U.S. at 726-27, 89 S. Ct. 1394. Some detentions do not amount to "arrests" requiring probable cause, but rather constitute less-than-arrest "seizures" subject to a less-than-probable-cause requirement for justification. See, e. g., Adams v. Williams, 407 U.S. 143, 145-46, 92 S. Ct. 1921, 32 L. Ed. 2d 612 (1972). Nonetheless, any "seizure" of the person that does not meet the Fourth Amendment standard of reasonableness may taint a subsequent statement or search. See, e. g., United States v. Robinson, 535 F.2d 881 (5th Cir. 1976); United States v. Rias, 524 F.2d 118 (5th Cir. 1975).

At the same time, courts have been careful to distinguish encounters with police undertaken by a person voluntarily from Fourth Amendment "arrests" or less-than-arrest "seizures." Thus, in Davis v. Mississippi, supra, where it held that an "investigatory detention" without probable cause violated the Fourth Amendment, the Supreme Court took pains to point out that the "State makes no claim that petitioner voluntarily accompanied the police officers to headquarters . . ." 394 U.S. at 726, 89 S.Ct. at 1397. Similarly, in Morales v. New York, 396 U.S. 102, 90 S. Ct. 291, 24 L. Ed. 2d 299 (1969), where petitioner claimed that his stationhouse confession was tainted by an illegal seizure of his person, the Court remanded for an evidentiary hearing, on inter alia, the question whether petitioner's "confrontation with the police was voluntarily undertaken by him . . ." Id. at 105, 90 S.Ct. at 293. Again, in Cupp v. Murphy, 412 U.S. 291, 93 S. Ct. 2000, 36 L. Ed. 2d 900 (1973) the Court noted that even though respondent "telephoned the Portland police and voluntarily came into Portland for questioning," id. at 292, 93 S.Ct. at 2002, the police refusal to let him leave when he wanted to marked the beginning of a "detention of the respondent against his will (and) constituted a seizure of his person," id. at 294, 93 S.Ct. at 2003. See also Adams v. Williams, 407 U.S. 143, 146 & n.1, 92 S. Ct. 1921, 32 L. Ed. 2d 612 (1972); United States v. Johnson, 147 U.S.App.D.C. 31, 452 F.2d 1363, 1371-72 & n.36 (1971), appeal after remand, 158 U.S.App.D.C. 299, 485 F.2d 1078 (1973), cert. denied, 415 U.S. 923, 94 S. Ct. 1426, 39 L. Ed. 2d 478 (1974); United States v. Bailey, 447 F.2d 735, 737 (5th Cir. 1971); United States v. Holland, 438 F.2d 887, 888-89 (6th Cir. 1971); Doran v. United States, 421 F.2d 865, 868-69 (9th Cir. 1970); Government of Virgin Islands v. Kirnon, 377 F. Supp. 601, 698-99 (D.V.I.1974). As the cases cited above make plain, a person is not arrested or seized under the Fourth Amendment if he is free to choose whether to enter or continue an encounter with police and elects to do so.13

Turning to the facts in this case, we find the district court did not err in holding that Brunson was not seized when he accompanied investigators to the 33rd Street Annex. The evidence supports the view that the investigators had not focused on "Black Boy" as a suspect, let alone obtained information sufficient to support probable cause as to him, when they went to talk to him. The investigators testified, and we see no reason to doubt, that they simply wanted to interview anyone who might know the whereabouts of Glen Herman, upon whom the investigation had focused. Significantly, the investigators told Brunson that he was not under arrest, that they intended to drive him home after the interview, and that they wanted his decision whether to talk to them to be voluntary.14 They certainly did not treat Brunson as if he were under detention: there was no frisk, no handcuffing, and no physical contact of any kind. They testified, and we see no reason to doubt, that they would have taken Brunson home if he had asked them to, any time before he implicated himself. In short, from all that appears, the investigators were careful not to restrain Brunson's "freedom to walk away."

Even if we were to credit Brunson's testimony that he thought he was being arrested, our conclusion would be the same. Brunson knew what the investigators did not, that he had been present at the robbery and killing. His statement at the Annex, note 6 supra, suggests that he had been expecting police to come for him and simply had waited for them; hence, it would not be surprising if he did think the investigators had come to arrest him. But they did not come for that purpose, and they told him so. Under these circumstances, Brunson's own expectations cannot convert an otherwise innocent request to talk to investigators into a Fourth Amendment "seizure." See United States v. Scheiblauer, 472 F.2d 297, 301 (9th Cir. 1973); United States v. Kershner, 432 F.2d 1066, 1070 (5th Cir. 1970); United States v. Cortez, 425 F.2d 453, 457 (6th Cir.), cert. denied, 400 U.S. 906, 91 S. Ct. 147, 27 L. Ed. 2d 143 (1970); Coates v. United States, 134 U.S.App.D.C. 97, 413 F.2d 371, 373-74 (1969); Hicks v. United States, 127 U.S.App.D.C. 209, 382 F.2d 158, 161 (1967). We hold that the district court did not err in finding that Brunson decided to accompany the investigators without pressure on their part and in therefore refusing to suppress the statement and fingerprints.

III. OTHER CRIME EVIDENCE.

Brunson argues that the district court erred in permitting the government, over objection, to present evidence at the end of its case in chief that four days before the Gotha robbery and murder, Brunson and Glen Herman robbed a Magik Market grocery in Winter Garden. On the government's proffer, and out of the presence of the jury, Mary Ellen Gardner testified that on the evening of July 17, 1975 she was working behind the counter of the Magik Market when two black men forced her to open the store's safe at gunpoint. The men fled with two bags of money from the safe and Gardner's purse, which contained an elk's tooth necklace, some food stamps, a small amount of cash, and other personal effects. Gardner stated that a few days later her wallet was found beside the road between Winter Garden and Apopka and returned to her, and that she herself found some of the purse's other contents scattered along the same road. She said that one of the men who robbed her had dropped a dollar bill, a book of matches, and a small photograph onto the counter when, before robbing her, he feigned interest in buying a cinnamon roll. Gardner was unable to describe or identify the men who committed the robbery.

Marilyn Conyers who had known both Brunson and Glen Herman for some time, testified that she had been riding with them in Herman's Cadillac on the evening of July 17, 1975. Brunson, she said, was wearing a gun in a shoulder holster. They rode around a while and Conyers fell asleep in the back seat. When she awoke, the car was parked behind the Magik Market, and Brunson and Herman were climbing back in. Herman was carrying a gun, some money, and a woman's purse. Brunson, she testified, stated that Herman had held a gun to the woman's head. The three of them drove to Apopka, and on the way Conyers looked inside the purse and saw a necklace with a tooth on it, some food stamps, a small amount of cash, and other personal effects. She threw the contents of the purse out the car window and, when they arrived at Apopka, Brunson and Herman divided up the money.

Brunson's mother identified the picture left behind by the robbers as one of her granddaughter (and Thomas Brunson's niece) from New York.

After hearing this evidence on the government's proffer, the court looked to the four-prong test for deciding admissibility of evidence of other crimes outlined in, e. g., United States v. San Martin, 505 F.2d 918, 921-22 (5th Cir. 1974) and United States v. Goodwin, 492 F.2d 1141, 1148-55 (5th Cir. 1974), and it held that the evidence was admissible for the sole purpose of showing that when Brunson entered the Gotha post office, he intended to help Herman rob it. Record Vol. V at 873-76. Then, after admonishing the jury carefully as to the limited purpose for which the evidence would be admitted, id. at 961-62, the court allowed the same three witnesses to present substantially the same testimony to the jury.15

The general rule against admitting evidence of crimes or wrongs by a defendant, other than those for which he is on trial, is intended to prevent a jury from convicting a defendant "because it believes him to be a person of bad character or because of a notion that, since he committed some other similar crime, he must also have committed the crime for which he is on trial." United States v. Goodwin, supra, 492 F.2d at 1148. Although there are circumstances under which the trial court properly may permit evidence of other crimes to be introduced,16 the court first must satisfy itself that several conditions designed to protect the general rule from erosion are met:

1. Proof of the prior similar offenses must be 'plain, clear and convincing;'

2. The offenses must not be too remote in time to the alleged crime;

3. The element of the prior crime for which there is a recognized exception to the general rule, such as intent, must be a material issue in the instant case;

4. There must be a substantial need for the probative value of the evidence provided for by the prior crimes. (cite). If all of these prerequisites are satisfied, and if it appears on balance that the need for such evidence outweighs the prejudicial effect it is likely to have, then the evidence is admissible.

United States v. San Martin, supra, 505 F.2d at 921-22 (emphasis in original).17

A. Scope of Cross-Examination on Proffer. Brunson stresses that Conyers' testimony, otherwise damning, was subject to attack on the ground of credibility; and that absent this testimony, no witness could connect him with the Magik Market robbery. He argues that during the proffer the district court unduly limited his cross-examination of Conyers as to grants of immunity she may have received. The result, he complains, is that he was unable to convince the court that the evidence of his participation in the Magik Market robbery was not "plain, clear and convincing" because Conyers was not a credible witness.

On the proffer the government represented, and Conyers testified, that she had been granted immunity from state prosecution for the Magik Market robbery. Record Vol. V at 839-41, 864-65. The government also represented that she had not been granted immunity from federal prosecution, id. at 839, although later, on cross-examination before the jury, Conyers testified that she had been arrested in connection with the Gotha crimes and that those charges had been dropped. Id. at 1013-15.18 Brunson's specific complaint is that the district court did not permit him to pursue the topic of immunity for the Gotha crimes on cross-examination during the proffer. See id. at 841-42, 863-64.

We think the complaint is without merit. The district court knew about the state grant of immunity when it ruled on admissibility, and it may have known about any federal grant. See note 18 supra. In any event, on the second day of the proffer the court did permit defense counsel to ask Conyers whether she was testifying because of a grant of immunity, and the court itself questioned her with regard to the truthfulness of her testimony. Record Vol. V at 863-65. The scope of cross-examination ordinarily is committed to the sound discretion of the trial court, United States v. Killian, 541 F.2d 1156, 1161 (5th Cir. 1976), and we cannot say that discretion was abused in this instance. Moreover, the defense was permitted to cross-examine Conyers fully on these matters during her testimony before the jury, Record Vol. V at 1009-15, so that any error on the proffer would, in our opinion, become harmless. Fed.R.Crim.Pro. 52(a).

B. Admission of Evidence. We also conclude that the district court did not err in admitting the evidence described above. Although Gardner could not identify the two armed black men who robbed her Conyers' testimony that it was Brunson and Herman was corroborated in a number of other details.19 The testimony of Brunson's mother that the photograph left by one of the robbers, apparently inadvertently, was of Brunson's niece also had some corroborative value. We cannot say on this record that the district court erred in holding the evidence of Brunson's participation in the Magik Market robbery was "plain, clear and convincing."We also think that the two robberies both committed by two men with a gun and in the absence of witnesses other than the victim were sufficiently similar to support admissibility here. See United States v. Fonseca, 490 F.2d 464, 470-71 (5th Cir.), pet. for rehearing granted and case remanded for resentencing. 5 Cir., 497 F.2d 1384, cert. denied, 419 U.S. 1072, 95 S. Ct. 660, 42 L. Ed. 2d 668 (1974); United States v. Broadway, 477 F.2d 991, 994-95 (5th Cir. 1973). The time span of four days between the two crimes certainly did not render the Magik Market robbery "too remote in time" from the Gotha robbery and murder to support admissibility. See United States v. Arteaga- Limones, 529 F.2d 1183, 1197-98 (5th Cir. 1976); United States v. San Martin, supra, 505 F.2d at 922-23.

Finally, as the case developed, the only genuine issue was whether Brunson harbored the requisite intent to help Herman rob the Gotha post office. In his statement to investigators, which was placed in evidence before the other crime evidence, Brunson admitted that he was with Herman in the post office when the crimes took place and denied only that he, Brunson, had any idea Herman was going to commit a robbery. Brunson reiterated the story throughout his later testimony at trial. The government clearly had a substantial need for evidence that Brunson had helped Herman rob the Magik Market four days earlier, for there was precious little other evidence to contradict Brunson's claim of an innocent, unknowing state of mind. We hold that the district court did not abuse its discretion in concluding that the need for this evidence outweighed its admittedly prejudicial tendency.20

IV. SUFFICIENCY OF THE EVIDENCE.

Brunson's argument that the evidence was insufficient to support conviction rests on his argument that the other crimes evidence should have been excluded. Brief for Appellant at 38-39. We already have rejected the latter argument. We also have reviewed the lengthy record in this case and, viewing the evidence in the light most favorable to the government, Glasser v. United States, 315 U.S. 60, 80, 62 S. Ct. 457, 86 L. Ed. 680 (1942), we hold the evidence was sufficient to support conviction.

AFFIRMED.