The Volokh Conspiracy

Mostly law professors | Sometimes contrarian | Often libertarian | Always independent


The overlooked audiotape of the Michael Brown shooting


A major story from The Post Sunday began by noting that "[n]o video of the [Michael Brown shooting] has emerged, leaving the nation, like the grand jury that completed its work two weeks ago, dependent on a vast encyclopedia of evidence, a mountain of witness statements, forensic reports and police narratives." The Post story is a very useful summary. And the conflicting conclusions about the Brown case contrast with the Eric Garner case, where a videotape of an apparent chokehold arrest has led commenters on the both the left and the right to raise concerns about the police actions there.

So far overlooked in all recent Brown media coverage, however, is an important piece of evidence: an audiotape of the Brown shooting. The grand jury listened to the tape, giving them incontrovertible evidence about the timing of the shots. Yet the audiotape does not appear to have been among the documents released by the St. Louis County Prosecuting Attorney's Office. [UPDATE, Tuesday, Dec. 9: The audiotape was released on Monday, Dec. 8. See above.] As a result, the tape has been ignored in discussion about the grand jury's decision. But the audiotape—combined with the forensic evidence from the scene—provides powerful corroboration of Officer Wilson's testimony that Michael Brown was charging him.

The basic outlines of the Michael Brown shooting are well known. (Interested readers can also review my posts on Officer Wilson's testimony, the physical evidence, Witness 10's testimony, and Dorian Johnson's implausible story.) A critical point of dispute has been whether Michael Brown was "charging" towards Officer Wilson, as several highly credible witnesses (such as Witness 10) testified. To determine the speed with which Brown was moving toward Officer Wilson, two data points are required: the distance over which he moved and the time it took for him to cover that distance. Speed = distance ÷ time.

Let's turn first to the time involved in the shooting. Here's where the overlooked audiotaped evidence comes in. As first reported by CNN, at exactly the time Brown was shot, a man was using a streaming video technology, called Glide, to record a message to his girlfriend. You can listen to the actual message here and can hear 10 apparent shots in the background. The message was sent at 12:02:14 p.m. (Central Daylight Time) on Saturday, Aug. 9, 2014. Once sent and recorded on Glide's servers, a time stamp blocked editing or other alterations.

Figure 1—Acoustic pattern of shots. Source: Shotspotter.

In the grand jury, the witness who made the tape authenticated it as accurate, and prosecutors then played the tape (vol 19: 265:3). What the grand jury heard on the tape has been explained by Dr. Bob Showen and Paul Greene, of SST, Inc. (a/k/a Shotspotter). Their acoustic pattern is depicted in the adjacent chart.

It is a simple matter to listen to the shots and calculate the time that elapses. Showen and Greene precisely calculated that "[t]here is a total elapsed time of 6.5 seconds over the 10 shots. Two volleys, the first of 6 shots and second of 4, are separated by approximately 3 seconds." While the grand jury apparently did this calculation on its own, for convenience I report the times as calculated by Showne and Greene in the adjacent Table 1. (The chart also depicts echo information, showing a relatively constant echo.)


This incontrovertible acoustic evidence allowed the grand jury to differentiate testimony that was not credible from testimony that was. In an earlier post, I discussed at length Witness 10's testimony, which I find to be particularly persuasive. Witness 10's testimony can be measured against the yardstick of the acoustic evidence. Witness 10 told police, and later the grand jurors, that Wilson initially fired "five to six shots" (vol. 6, 182:14). That matches the audiotape, which showed six initial shots. Witness 10 then reported that as Wilson was firing, Brown came to a stop—having been hit perhaps once because Brown flinched once (183:17). As Brown stopped moving, Wilson stopped shooting. Witness 10 said that Wilson stopped for "maybe two seconds" (184:9). But then Brown began "charging" again, and Officer Wilson responded with more shots (184:16). Witness 10 estimated that the number of shots this time was "three to four"—matching the four shots identified on the audiotape, as well as the fact of a pause between the two volleys.

So far the audio evidence alone provides strong corroboration for Witness 10's testimony about the number and pattern of shots. But what about the testimony that Brown was "charging." To calculate speed, we need to know the distance that Michael Brown covered while the shots were being fired. Clear physical evidence allows at least a rough calculation of the distance that Michael Brown moved towards Officer Wilson. Michael Brown's tragic ending point is known, as his body marked that spot. And we also know from the Medical Examiner's testimony that the final shot to the top of Brown's head would have been "immediately incapacitating" (vol. 3, 170:7).

To determine Michael Brown's starting point, we have to rely on a combination of physical evidence and eyewitness testimony. Immediately after the shooting, investigating police obtained witness statements and placed an orange cone down Canfield Drive where they thought Michael Brown had gone, depicted in Figure 2 (grand jury exhibit 105).

Figure 2—Baseline evidence cone. Source: St. Louis County Prosecuting Attorney's Office.

They placed the cone there because "[a]s best we could tell based off witness accounts, that would have been the furthest point east that Michael Brown would have went to. So that would be the intersection of roughly Coppercreek Court and Canfield Drive" (vol. 24, 30:25), which is where a road branches off Canfield Drive to a parking area next to a large building (2943/2947 Copperfield Court). Also notice the light post, which is surrounded by memorials to Michael Brown.

It may help to see the relation of the intersection to Michael Brown's final position by looking at this later-taken shot, looking down Canfield Drive toward the light post and intersection from where Michael Brown's body was found (Figure 3).

Figure 3—View down Canfield. Source: St. Louis County Prosecuting Attorney's Office.

The police placed the cone in this spot shortly after the shooting based on the contemporaneous information they were receiving. Has anything surfaced since the shooting to call the placement into doubt? One way to assess this issue—and to give Brown the benefit of the doubt —is to use the testimony of his best friend, Dorian Johnson. Johnson apparently places Brown on the street next to the large building on 2943/2947 Copperfield Court. Johnson testified that Brown "was barely on the sidewalk, he was barely on the sidewalk to the parking lot. He was going towards this building. I presume that's the way he was running. He wasn't really all the way on the driveway when the . . . shot went off, and he turned around, and he was in the street" (vol. 4, 158:15). Another witness, Witness 14 (again, a witness sympathetic to Brown who thought he was trying to surrender) was even more specific. She said in her first police interview (Aug. 12) that Brown "was still standing . . . partially on the parking lot and on the grass." (Interview 14-1, at 3-4.) Later in that same interview, she said that "[w]hen [Brown] turned around he had about one foot on the grass and one on the driveway." (Id. at 16.)

Relying on this testimony and the placement of the cone permits a calculation of the distance that Michael Brown traveled back towards Officer Wilson, to where he was finally killed. The police used the cone as the "baseline" for further measurements back up the street—point O for measuring where they found the evidence that they gathered. For example, the evidence report identifies Brown's left foot as ultimately coming to rest 48 feet, 2 inches back up Canfield from the cone. So if Dorian Johnson and Witness 14 are believed, then Brown moved more than 48 feet back towards Wilson.

trail of blood-vert
Figure 4—Trail of blood on Canfield. Source: St. Louis County Prosecuting Attorney's Office.

Some physical evidence confirms that Michael Brown generally followed the path from the area of the cone to his final resting point. Investigating police officers found in the street what was later identified as spots of Michael Brown's blood—denoted by evidence markers 19 and 20 (vol. 24, 88:6). The blood spot identified by evidence marker 20 is 26 feet, 7 inches back up Canfield from the cone—or approximately 22 feet away from where Michael Brown's body was found, as shown in the adjacent crime scene photograph (Figure 4).

The blood spatter also shows direction—specifically that Brown was moving towards Wilson—as is apparent from the physical appearance of the spots. (This commonsense conclusion is confirmed by experts. For example, Sunday's story in The Post quotes Michael F. LaForte, a Florida-based forensics expert who examined the investigative reports, as concluding that "[b]lood strikes the ground and then radiates out in the direction he was traveling.") So the physical evidence shows Brown moved at least 22 feet generally away from the cone and towards Wilson.

These various pieces of information can be used to roughly calculate Brown's speed. The 6.5 seconds that elapse on the audiotape from the first shot to the tenth (and final) shot provides some sense of time. And using Dorian Johnson's testimony (as one way of giving Michael Brown the benefit of the doubt), the first shot "literally stopped [Brown] in his tracks and [he] turned around at that point" (vol. 4, 158:4). So according to Dorian Johnson's account, Brown would have had 6.5 seconds to travel from where he turned around back to the point where we was finally killed—a total distance of 48 feet (the distance from the marker cone to his left foot). To again give the benefit of the doubt to Michael Brown, this calculation ignores the fact that the baseline of 48 feet is parallel to the street, while Brown was moving somewhat farther—i.e., diagonally towards the middle of the street. Conservatively calculating (by, for example, ignoring the likelihood that Brown paused—an issue discussed below), this works out to average movement of about 7.4 feet per second—very brisk movement. (For comparison, walking 3 miles per hour converts to 4.4 feet per second.)

Most important, starting from standing stop would produce a peak speed of more than the average speed—i.e., more than 7.4 feet per second. According to Johnson, Brown had to turn around before he could even begin moving towards the officer (vol. 4, 157:6). So even under Dorian Johnson's testimony, Brown would have been moving very rapidly towards Wilson—contrary to the overall impression that Johnson tries to create. Indeed, Johnson even goes so far as to claim that Brown got only "half a step maybe" toward the officer (vol. 4, 157:13).

Compare Johnson's testimony with Witness 10's testimony. Witness 10 told police on Aug. 11 (two days after the shooting)—and later the grand jury—that Brown ran down Canfield Drive, made it to intersecting street, and then turned around and came back towards Wilson (vol. 6, 179:13). Witness 10 said that Brown was in a "full blown" charge towards Wilson and that Wilson fired when Brown was about 30 feet away ("10 yards," at page 12 of the interview), and that at least one of the shots in the initial volley hit Brown.

Making the assumption that the two blood spatters (evidence markers 20 and then 19) occurred during the pause in the shooting—as seems plausible, given the time needed for blood to begin to flow from a wound—and then that Brown paused and began moving shortly before Wilson fired his first shot in the last volley, then Brown would have covered the distance between those spots and where his body finally came to rest in about 1.7 seconds. Giving him the benefit of the doubt and using marker 19 (found 31 feet up Canfield Drive), Brown would have closed 17 feet in that time—an average forward movement of 10 feet per second, with a likely peak speed of greater than that, since Brown had paused to some degree and thus his forward movement had to accelerate.

Officer Wilson's own testimony also generally matches the audiotape. In his interview on Aug. 10 (the day after the shooting), Wilson said he fired a series of shots, then he "paused for second" and then resumed firing. Later in his FBI interview on Aug. 28, Wilson said that after a series of shots, Brown stopped briefly, but then started running at him again (vol. 5, 168:5). In his testimony before the grand jury, Officer Wilson gave more details. He testified that he pursued Brown down Canfield and that Brown stopped when he was "at that light pole"—i.e., the light pole depicted in the photograph above with tributes to Michael Brown around it (vol. 5, 227:3). Brown then turned, did a stutter step, and then started "running" toward Wilson (227:13). According to Wilson, he fired a "series of shots"—he wasn't sure exactly how many (228:1). Wilson testified he then told Brown to get on the ground, Brown didn't, and then he fired "another round of shots" (228:15). These shots didn't work to stop Brown, who looked like he was "bulking up" to run through the shots (228:20). So Wilson fired "at least once," he couldn't recall how many, and managed to hit Brown in the head and bring him down (229:19). Wilson's account is thus that there was some sort of a break in the continuous action (Brown's "bulking up") that conforms to the three second gap in the shots before what was the final and fatal volley.

The grand jury clearly recognized the significance of the audio evidence. In the last volume of grand jury, one of the grand jurors questioned the crime scene detective about the time that passed between the shots, saying "[w]e tried to approximate it, it was six or seven seconds, but do you know exactly?" (vol. 24, 88:25). The detective did not know, but the prosecutor referred to an FBI analysis (from Quantico) that confirmed that the sounds were apparent gunshots. A grand jury asked whether the FBI had constructed an exact a time line, and the prosecutor said it had not. That FBI report has apparently not been made public; I haven't been able to locate it in the on-line sources I have examined.

I've tried to work through these speed calculations in some detail not because they can provide ironclad proof of the precise speed that Brown was moving towards Officer Wilson, but rather because the general picture from the grand jury evidence is unmistakable: Brown was clearly not taking just a "half a step" towards the officer and trying to surrender; rather, he was moving rapidly towards the officer over an extended distance. And the grand jurors were clearly clued into the significance of the audiotape and related forensic evidence as they made their decision. That evidence strongly supported the conclusion that no charges were appropriate. The grand jury could have quite reasonably determined that Wilson faced a man who had fled arrest and then circled back and "charged" him—i.e., moved rapidly and purposefully toward him in the face of repeated gunfire.

I hope that more people interested in the Michael Brown shooting will consider the evidence described in detail here. As was widely recognized last week, both conservative and liberal observers raised questions about Eric Garner's death based on a single piece of evidence—the videotape of his arrest. That hasn't happened yet in the Micheal Brown case, purportedly because comparable evidence is unavailable in the Brown case. As Paul Waldman wrote in The Post: "The biggest difference between Garner's case and that of Michael Brown in Ferguson, Missouri, is the existence of videotape showing exactly what happened to Garner. When there isn't that kind of undeniable proof, everyone is able to write their own story about what happened."

Everyone should not be allowed to "write their own story" about the Michael Brown shooting. An audiotape of the shooting exists, as well as substantial related physical evidence. And yet I have seen very little discussion of this evidence, particularly from Michael Brown supporters. Many seem to be more interested in discussing "the lessons of Ferguson" or some other broad topic. Indeed, some of Brown's supporters candidly concede that the facts are irrelevant. But for those who want to know whether the grand jury reached the right conclusion, the facts are paramount. The grand jury had an audiotape and ample other evidence to support the conclusion that Michael Brown directly charged Wilson—and thus that no charges were appropriate.