Ejected Shell Casings Can’t Reliably Tell Much About a Shooter’s Location

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Nearly 8,000 rounds fired by Los Angeles County (CA) sheriff’s deputies have now conclusively proved what the Force Science Research Center first asserted more than 2 years ago: The single greatest influence on where spent shell casings land when ejected from a semiautomatic handgun is how the pistol is physically manipulated by the shooter, not any rigid, intrinsic mechanical factor.

Indeed, the FSRC’s benchmark findings show that the ejection spread can vary up to 24 feet with the same gun, fired by the same shooter, depending on how the weapon is gripped and moved, according to the Center’s executive director, Dr. Bill Lewinski of Minnesota State University-Mankato.

FSRC’s scientific testing can have a significant impact in officer-involved shootings where LEOs are accused of lying about where they were positioned during a confrontation, based on where their ejected shell casings were found.

Just last week, for example, Lewinski testified on behalf of a federal agent in a major Eastern city who shot and killed an offender with a history of assaulting police officers who tried to drive into him during an off-duty traffic altercation. The agent was charged with intentional murder.

At trial, prosecutors, supported by a firearms and tool mark expert, framed the traditional argument that each model of semiauto handgun has an established ejection pattern, determined by the position of the ejection port and the internal mechanics of the weapon. A shooter’s location when firing can be calculated by where spent casings land, the prosecution team claimed. In this case, where the agent’s ejected casings were found cast doubt about where he said he was standing–in a position of jeopardy–when he shot.

However, Lewinski was able to present his fresh findings from the Los Angeles County study in his testimony as a defense expert. These soundly refute the concept of reliable, predetermined ejection patterns. When Lewinski finished explaining the scientifically documented reality, the prosecutors declined to engage in any cross-examination.

The new study, the most extensive ever undertaken of ejection patterns, involved 48 LASD deputies firing a total of 7,920 rounds across 2 weeks last month [5/05] at the department’s range under conditions closely monitored by Lewinski and another FSRC representative, Dave Karwoski.

Collectively the deputies completed 72 “trials” (tests), each consisting of firing 110 rounds through a particular gun. The guns used were 9mm Berettas and Glocks, .40-cal. Sig-Sauers and .45-cal. H&Ks, common law enforcement handguns. The shooters held the guns in 11 different hand grips and angles, including the barrel pointed slightly down, pointed slightly up, parallel to the ground and canted at various angles up to 90-degrees off-center. On some of the tests, the officers also moved the gun as they were shooting.

Although each gun had a supposedly “predictable” ejection pattern, “how the gun was held and manipulated had a significant and dramatic effect on the actual angular displacement of its spent shell casings and the distance they landed from the shooter,” says FSRC Deputy Director Bill Hudson, who is coordinating a minute analysis of the study’s results.

“Regardless of the gun, we documented the same phenomenon,” Lewinski says. Namely: as grip and positioning of the gun changed, so did the ejection “pattern.” With each type of gun, spent casings landed in all four quadrants radiating from the shooter’s location.

“We found that by manipulating a gun as officers actually do in real shooting situations, the placement of ejected shell casings changed across a broad range–from 12 feet to a shooter’s right rear to 12 feet to his left front, a total span of 24 feet,” Lewinski says.

“With each type of gun, shells landed at varying distances to the shooter’s right rear, 90 degrees to his right, directly in front of him, 90 degrees to his left and to his left rear–in short, everywhere! In some cases, even with the same gun held in the identical position by the same shooter, the places to which spent shells were ejected were as much as 10 feet apart. That’s with grip, ammo, everything the same.”

The ejection pattern of the Glock was most influenced by manipulation of the gun, Lewinski found, the Colt least so. “But even then, there could be a dramatic variance.”

The bottom line, Lewinski asserts, is this: “This study proves beyond doubt that the most significant factor determining where spent shell casings land is how the gun is held and moved by the officer when firing. There is no mechanical element associated with ejection that can have that radical an effect.”

Greg Karim, forensic firearms examiner for the Austin (TX) P.D. and a member of FSRC’s Technical Advisory Board, agrees. He points out that there are a multitude of mechanical factors that can influence how and where casings are ejected, including lubrication of the slide, condition of the ammunition, cleanliness and maintenance of the chamber area, condition of the magazine spring and lips, spring tension in the extractor and so on.

“But without doubt,” he says, “the mechanical factors are of minimal influence compared to how the gun is held and manipulated.”

Ideally, he adds, there is consistency in a shooting situation. “You know the gun, you know the shooter, you have eye witnesses and the placement of expended shells puts the officer just where he said he was.” But when there are inconsistencies, “the investigator must put appropriate weight on shell casing placement, given other factors in the situation. And when you don’t know how the gun was manipulated, shell casing placement could be of zero value.”

Tom Aveni, an internationally known firearms authority and a member of FSRC’s National Advisory Board, considers the new study’s findings from a trainer’s perspective. “Having trained police officers in handgun skills for over 22 years and having been personally exposed to the ejection of roughly 1.5 million pistol cartridges, I know there are many salient factors that bear on where ejected shells land. It’s rare to see 2 people pick up the same handgun, fire the same ammunition, and not have measurable deviations in their cartridge case ejection patterns.

“On the street, we’re likely to see a plethora of improvised shooting postures. In lethal confrontations, officers routinely find themselves firing when off-balance, or worse yet when falling.

“If the officer is firing around cover or concealment, the handgun is likely to be canted in a way that will also influence ejection patterns. The officer might find himself or herself firing from a seated or prone position, perhaps with the handgun resting against a surface or object. Or the officer might exhibit a crouching posture far in excess of anything exhibited in training. We should also take into consideration officers firing when moving, climbing stairs or struggling for retention of their weapon.”

All this considered, Aveni is appalled that an officer’s deadly force decision-making can be challenged and the officer criminally prosecuted on the basis of ejected shell casings. He calls this “bad science and misplaced faith.”

For an essay by Aveni of the same title, visit:


Yet such a prosecution is what got Lewinski interested in studying ejection patterns in the first place. Based on the placement of a single ejected shell, an officer in Arizona was accused of lying about an unjustified use of deadly force in the fatal shooting of a female suspect that the officer claimed tried to run over him with her car (“chillingly similar” to the more recent Eastern case involving the federal agent, Lewinski observes).

Rudimentary testing that Lewinski did with the officer on an Arizona range and with other subjects at FSRC headquarters in Minnesota in 2003 strongly suggested that gun manipulation could be the decisive factor in where ejected shells ended up. Lewinski’s testimony about those findings was considered instrumental in acquitting the officer of murder.

To confirm the preliminary results from those studies, Lewinski launched the broader investigation with the cooperation of the Los Angeles County Sheriff’s Dept. and Sheriff Leroy Baca. Detailed results of the testing will be published later this year in an issue of FSRC’s forthcoming e-journal, now in development.

Meanwhile, Lewinski expresses his deep appreciation to the deputies who participated in the latest study, and to others who helped make the research successful.

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