NOT PRECEDENTIAL

UNITED STATES COURT OF APPEALS

FOR THE THIRD CIRCUIT

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15-4062

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UNITED STATES OF AMERICA

v.

MARCUS WALKER,

 Appellant

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On Appeal from the District Court

for the Eastern District of Pennsylvania

(E.D. Pa. 2-13-cr-00391-002)

Honorable Legrome D. Davis, U.S. District Judge

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Submitted Under Third Circuit L.A.R. 34.1(a)

January 23, 2018

Before: JORDAN, KRAUSE, and ROTH, Circuit Judges

(Opinion filed: June 5, 2019)

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OPINION*

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* This disposition is not an opinion of the full Court and pursuant to I.O.P. 5.7 does not 

constitute binding precedent.
1

KRAUSE, Circuit Judge.

Appellant Marcus Walker challenges his convictions for conspiracy to commit 

Hobbs Act robbery in violation of 18 U.S.C. § 1951(a), attempted Hobbs Act robbery in 

violation of 18 U.S.C. §§ 1951(a) and 2, and using and carrying a firearm during and in 

relation to a crime of violence in violation of 18 U.S.C. §§ 924(c) and 2. For the reasons 

stated below, we will affirm. 

I. Background

This case stems from a robbery in which Walker acted as the lookout. While 

Walker waited in a car, two of his accomplices robbed a house, one holding a boy at 

gunpoint. All of Walker’s codefendants pleaded guilty to various counts, and Walker 

alone went to trial. 

At trial, the Government presented testimony from three cooperators who were

involved in or knew about the robbery and from Agent Patrick Henning, the lead 

investigator on the case. In addition to testifying about proffer sessions he had with two

cooperating witnesses, Agent Henning spoke at length about cell phone records and cell 

site location information (CSLI) associated with cell phones from the investigation.

1

With respect to the cell phone records, Agent Henning testified that an analyst 

extracted data from cell phones seized from two of the cooperators, which yielded contact 

lists, call records, and text messages. In addition, the Government obtained through 

 

1 CSLI identifies the cell towers to which a cell phone connects at certain times, 

thereby allowing the Government to determine the cell phone’s approximate location at 

the time of connection. See Carpenter v. United States, 138 S. Ct. 2206, 2211–12 (2018).
2

subpoena “call detail records” from the phone companies for those same phones, which 

included “pages and pages of phone records that list, with timestamps, calls that are made 

in sequential order,” as well as subscriber information. App. 686. From this information, 

Agent Henning and an analyst organized certain data into slides depicting phone contacts 

that the codefendants made to one another during the relevant time frame. 

As for the CSLI, Agent Henning created a series of maps that identified “points of 

interest” in the case, such as the location of the robbery target and the latitude and 

longitude of the cell towers to which Walker’s cell phone had connected at pertinent 

times over thirteen days and to which a codefendant’s cell phone had connected at 

pertinent times over two days. When asked how CSLI worked, Agent Henning 

responded that he was not an expert in the technology but began to explain what he did 

know. Defense counsel objected on the ground that Agent Henning was not an expert

witness. 2 After some back and forth at side bar, the parties agreed that “just transposing

[onto a map] the latitude and longitude” of a cell phone tower to which a phone had 

connected—information provided by the phone companies—did not require expert 

analysis, and the Court allowed Agent Henning to proceed. App. 710–11. Agent 

Henning then explained how the CSLI placed Walker and an accomplice in locations that

were consistent with other information about the robbery. 

 

2 Notably, defense counsel did not object when Agent Henning explained, only 

moments before, that “[t]his data is cell tower locations, it’s where the phones that the 

men in this robbery were using, where these phones were communicating, which towers 

they were communicating with at certain parts—certain parts of certain days.” App. 706.
3

The jury convicted Walker on all counts but, in connection with the Section 924(c) 

charge, found him guilty of only using and carrying a firearm, not brandishing it. The

District Court sentenced him to 72 months’ imprisonment on the robbery counts and a 

consecutive term of 60 months on the Section 924(c) count. This appeal followed.

II. Discussion3

On appeal, Walker argues that the District Court committed reversible error by: 

(1) admitting the CSLI into evidence in violation of Carpenter v. United States, 138 S. 

Ct. 2206 (2018); (2) allowing Agent Henning to testify about the phone records and CSLI 

and improperly “vouch” for the credibility of the cooperating witnesses in doing so; and 

(3) permitting Walker’s Section 924(c) conviction to stand. Because Walker did not raise 

these objections before the District Court, we review only for plain error.4 See United 

States v. DeMuro, 677 F.3d 550, 557 (3d Cir. 2012). We find none.

A. Admissibility of the CSLI

Walker first argues that, under Carpenter v. United States, the District Court 

plainly erred when it allowed the Government to introduce CSLI that it had obtained 

without a warrant in violation of his Fourth Amendment rights. Although it is true that 

 

3 The District Court had jurisdiction pursuant to 18 U.S.C. § 3231, and we have 

jurisdiction pursuant to 28 U.S.C. § 1291.

4 Plain error exists when “(1) an error was committed (2) that was plain, and (3) 

that affected the defendant’s substantial rights.” United States v. Lopez, 650 F.3d 952, 

959 (3d Cir. 2011) (citation omitted). Even upon finding a plain error, an appellate court 

has discretion whether to grant relief but should correct the error if it “seriously affect[s] 

the fairness, integrity or public reputation of judicial proceedings.” United States v. 

Olano, 507 U.S. 725, 736 (1993) (citation omitted).
4

law enforcement must generally secure a search warrant based on probable cause to 

obtain CSLI, see Carpenter, 138 S. Ct. at 2221, Walker’s argument is foreclosed by our 

recent decision in United States v. Goldstein, which held that the exclusionary rule does 

not apply where the government “had an objectively reasonable good faith belief that its 

conduct was legal when it acquired [the] CSLI.” 914 F.3d 200, 202 (3d Cir. 2019). As in 

Goldstein, the agents here relied on a then-valid judicial order, a then-valid statute, and 

then-binding appellate authority. Id. at 204. The District Court, therefore, did not 

commit any error, much less plain error, by admitting the CSLI into evidence.

B. Agent Henning’s Testimony

Walker next argues that the District Court committed plain error by permitting 

Agent Henning to testify about the phone records and CSLI because, Walker contends,

Agent Henning’s testimony was based on a report he did not create and therefore violated 

Walker’s Confrontation Clause rights under the Sixth Amendment. Walker also argues 

that Agent Henning improperly vouched for the testimony of the cooperating witnesses. 

We reject both arguments. 

The Confrontation Clause provides that “[i]n all criminal prosecutions, the 

accused shall enjoy the right . . . to be confronted with the witnesses against him.” U.S. 

Const. amend. VI. It bars “admission of testimonial statements of a witness who did not 

appear at trial unless he was unavailable to testify, and the defendant had had a prior 

opportunity for cross-examination.” Crawford v. Washington, 541 U.S. 36, 53–54 

(2004).
5

As to Walker’s Confrontation Clause argument, it is not clear that the District 

Court’s decision to allow Agent Henning to testify about the phone records or CSLI was 

error at all. The record contains evidence that Agent Henning personally reviewed the 

data at issue, even though he worked “[i]n conjunction with an . . . analyst.” App. 695; 

see, e.g., id. at 708 (“Q: What did you do with the cell site data? A: I reviewed . . . the 

information from the phone companies[.] I was able to see cell site latitude and longitude 

locations, which I can just go right into a Google Maps, for example, put in those points 

and see where those towers were.”). Thus, it appears that Agent Henning had an 

independent basis on which to testify about both the phone records and the CSLI.

5

 Cf. 

Bullcoming v. New Mexico, 564 U.S. 647, 662 (2011) (finding relevant to its conclusion 

that a Confrontation Clause violation occurred that the State did not contend that the 

testifying analyst—who did not perform the lab test at issue—had an “independent 

opinion” concerning the test results (citation omitted)).

Moreover, even assuming there was an error, it was not plain. There is very little 

case law concerning the proper bounds of CSLI testimony (as compared to, for example, 

testimony about forensic laboratory results) and nothing to suggest one must be a “cell 

site information analyst” to take the stand. Appellant Br. 21. This is especially true

where, as here, the parties agreed that the records themselves were admissible. 

Moreover, the Supreme Court’s Confrontation Clause jurisprudence, even as to forensic 

 

5 See App. 774 (“THE COURT: This was done in your presence, right, the work of 

the analyst, lest suggesting that - - AGENT HENNING: Yes, this was a collaborative 

effort.”). 
6

testing, could benefit from further clarification. See Stuart v. Alabama, 139 S. Ct. 36, 36

(2018) (Gorsuch, J., dissenting from denial of writ of certiorari) (observing that “[t]his 

Court’s most recent foray in [Confrontation Clause jurisprudence relating to forensic 

testing], Williams v. Illinois, 567 U.S. 50 (2012), yielded no majority and its various 

opinions have sown confusion in courts across the country.”).

Finally, the error—if there was one—was harmless. See United States v. Jimenez, 

513 F.3d 62, 78–79 (3d Cir. 2008). While Agent Henning’s testimony was important to 

the Government’s case, three cooperating witnesses testified that Walker participated in 

the robbery. In addition, as the Government notes, the defense engaged in a lengthy 

cross-examination of Agent Henning and did not challenge the accuracy of the data 

reflected on his slides or cite any discrepancies between the phone record exhibits and the 

underlying records. Thus, even though the phone records and CSLI were important 

corroborating evidence in this case, Walker cannot show prejudice, much less a 

miscarriage of justice on plain error review.

Walker’s vouching argument also fails. “Vouching constitutes an assurance by the 

prosecuting attorney of the credibility of a Government witness through personal 

knowledge or by other information outside of the testimony before the jury.” United 

States v. Walker, 155 F.3d 180, 184 (3d Cir. 1998). Although most often associated with 

prosecutors’ remarks in argument, vouching can also occur during witness examination. 

See United States v. Berrios, 676 F.3d 118, 134 (3d Cir. 2012). Here, Agent Henning 

testified about his proffer sessions with the cooperators and the cell phone data that he 

analyzed. His comments that the phone records and CSLI were “consistent with [his]
7

investigation,” e.g., App. 724, were not based “on information outside of the record,” 

Berrios, 676 F.3d at 134. To the contrary, Agent Henning testified about what he learned 

and how he learned it after the cooperators themselves had testified and been crossexamined about their versions of the events. While he acknowledged that the 

investigation did not utilize a wiretap or electronic surveillance, he explained that all 

records were obtained after-the-fact, and his analysis was based on them and his 

interviews with the cooperators. In short, Agent Henning spoke from personal 

knowledge and therefore was not vouching for the cooperating witnesses. See United 

States v. Christie, 624 F.3d 558, 569 (3d Cir. 2010) (holding that there was “no sensible 

vouching or bolstering challenge to be made” where the lead agent’s challenged 

testimony was based on his personal knowledge of the case). 

C. Conviction Under Section 924(c)

Finally, Walker argues that his conviction for using and carrying a firearm in 

connection with a crime of violence must be vacated because conspiracy and attempt to 

commit Hobbs Act robbery do not qualify as crimes of violence under the “elements 

clause” of 18 U.S.C. § 924(c)(3).

6

In addition, Walker contends that the District Court 

committed plain error because it is not clear whether the attempt count or the conspiracy 

count was the predicate offense for his Section 924(c) conviction. Neither argument is 

persuasive. 

 

6 Walker also argues that the residual clause is void for vagueness. Because we 

conclude that Walker’s Hobbs Act robbery is a crime of violence under the circumstances 

of this case, we need not address Walker’s challenge to the residual clause.
8

Section 924(c) provides for a mandatory minimum consecutive sentence where a 

defendant uses or carries a firearm during and in relation to a predicate “crime of 

violence.” 18 U.S.C. § 924(c)(1)(A). The statute defines a crime of violence in part as 

an offense that is a felony and “has as an element the use, attempted use, or threatened 

use of physical force against the person or property of another.” Id. § 924(c)(3)(A). The 

Hobbs Act defines “robbery” as “the unlawful taking or obtaining of personal property . . 

. against his will, by means of actual or threatened force, or violence, or fear of injury, 

immediate or future, to his person or property, or property in his custody or possession.” 

Id. § 1951(b)(1).

In United States v. Robinson, 844 F.3d 137, 143 (3d Cir. 2016), we held that a 

defendant’s contemporaneous convictions for Hobbs Act robbery and brandishing a gun 

in furtherance of it “necessarily support the determination that the predicate offense was 

committed with the ‘use, attempted use, or threatened use of physical force’” and, 

therefore, that the predicate offense constituted a crime of violence for purposes of 

Section 924(c). Given that Walker’s convictions were contemporaneous, Robinson

applies here.7 

Walker’s final argument about the alleged confusion regarding which count—

conspiracy or attempt—served as the predicate offense for his Section 924(c) conviction 

is belied by the record. In charging the jury on the Section 924(c) count, the District 

 

7 Walker contends that it is unclear whether Robinson applies to non-brandishing 

cases, but that very lack of clarity would foreclose a finding of plain error. See United 

States v. Dobson, 419 F.3d 231, 239 (3d Cir. 2005) (“In order to be ‘plain’ an error must 

be ‘clear’ or ‘obvious.’”) (citation omitted). 
9

Court told the jury that, in order to convict Walker on this count, it must find beyond a 

reasonable doubt “that the conspirator or the accomplice committed the crime of 

attempted interference with interstate commerce by robbery.” App. 885 (emphasis 

added). Breaking the charge down further, the Court continued, “So you would have to 

find . . . that during and in relation to the commission of that attempted Hobbs Act 

robbery, the Defendant or one of his accomplices or conspirators knowingly used or 

carried a firearm.” Id. (emphasis added). Because the Court clearly instructed the jury 

on the attempt count, we again find no error, plain or otherwise.

III. Conclusions

For the foregoing reasons, we will affirm the District Court’s judgment and 

sentence.