December 30, 2010

		Report: Significant inconsistencies in spent cartridge-case ejection By The Force Science Research Center

Contrary to persistent myth, where a cartridge case lands when it’s ejected from a semiautomatic pistol is not a reliable indicator of where the shooter was standing when the gun was fired. That fact has been scientifically confirmed by the Force Science Institute in a series of research experiments starting back in 2004. “Yet some investigators and firearms experts continue to use the location of spent casings as critical reference points in reconstructing shooting scenes,” says FSI’s executive director, Dr. Bill Lewinski.

“In the most tragic instances, this spurious ‘evidence’ has been cited in court to challenge officers’ statements about where they were positioned in controversial officer-involved shootings. And when such testimony is accepted as dependable, officers can suffer grave injustices.”

One example of a trial in which cartridge-case placement became a pivotal issue involved Arizona officer Dan Lovelace, whose courtroom ordeal, firing, and painful aftermath have been previously covered by Force Science and PoliceOne.

Now it will be easier for conscientious investigators, expert witnesses, and police attorneys to refute outmoded concepts about the importance of shell placement. Force Science findings on this subject have recently been given enhanced credibility with the publication of a peer-reviewed report on the Institute’s unique work in an academic journal, validating that the research methods employed were sound.

In a detailed article titled “Fired Cartridge Case Ejection Patterns from Semi-automatic Firearms,” authored by a research team led by Lewinski, the current issue of Investigative Sciences Journal showcases the emphatic results from one of FSI’s studies, involving more than 7,600 rounds cycled through the eight pistol models most commonly carried by LEOs.

These tests, the report states, “highlighted significant inconsistencies of spent cartridge-case ejection, compared to what is commonly expected and accepted.

The Journal is edited by Dr. James Adcock of the University of South Carolina and Dr. Henry Lee of the University of New Haven, with an editorial board of scholars from other institutions of higher learning in the U.S. and the United Kingdom. FSI’s research, Adcock states in an editor’s preface, “will be extremely helpful to those tasked with reconstructing shooting incidents.”

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LASD Study
The featured study was conducted in California at a range operated in “a small sheltered valley” by the Los Angeles County Sheriff’s Dept. Forty-five deputy volunteers participated. They ranged in age from 22 to 50 and had from two months to 28 years law enforcement experience.

Collectively, they fired 7,670 Winchester or Federal rounds from 9mm, .40-cal., and .45-cal handgun models: S&W 5906, Glock 17, Glock 21, Glock 23, Sig Sauer 226, Sig Sauer 229, H&K USP, and Beretta 92FS. These pistols are all designed to eject empty cases to the right rear.

Each deputy fired multiple rounds with gun held in 11 different positions. These covered a broad range of postures and manipulations: One- and two-handed grips at eye and waist levels while standing still and while turning; an awkward, improper two-handed hold that an officer might unintentionally achieve in rushing to get on target; inward, angled cants that sometimes occur when rotating and shooting; muzzle angled downward at a 22-degree angle and upward at 45 degrees; and so on.

All positions and movements studied have been “performed by police officers in dynamic, rapidly unfolding life-and-death shooting situations,” as discerned from investigations of OISs across 30 years, Lewinski says.

When shooting, each deputy stood by a stake in the center of a 30-ft. x 30-ft. test site, which was covered to a depth of 3 inches with carefully leveled, fine-grain river sand. “This reduced the bounce factor of the ejected cases to nearly zero,” Lewinski explains.

The 900-sq.-ft. area was gridded with colored string into 1-ft. square sections. To further pinpoint where ejected cases landed, researchers used transparent plastic templates with 1-in. grid marks that could be inserted into any square where cartridges fell.

The weather was “hot and still each testing day, so wind was not a significant factor in the test results,” Lewinski says. An earthen bluff served as a backstop for the shooting.

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Findings
“The results of this study demonstrated how unpredictable spent cartridge casing ejection patterns are,” the Journal report declares. The researchers documented “significant variability and uncertainty” about where a spent case “would come to rest” when ejected, the report says, emphasizing “the imprecision of identifying shooter location based solely on the location of a spent cartridge casing.”

For tabulation purposes, the gridded test area was divided into four quadrants that pin-wheeled around the shooter’s stake: right front and rear, and left front and rear. Lumping all test positions and firearms together, 73.6 percent of the spent cases fell into the quadrant right and rear of the shooter’s position.

“This confirms what experts cite as the location that spent cartridge casings should land in when ejected from the firearms used in this study,” the researchers note.

However, they point out, this means that over 2,000 casings — a significant 26.4 percent of those fired during the study — landed outside the anticipated “correct” area. Indeed, consistent with previous Force Science studies, cases fell within the entire 360 degrees — all four quadrants — surrounding the shooting position. The final resting places of some cases were more than 20 feet apart. And even those that settled within the right-rear quadrant were scattered widely within that area’s 225-sq.-ft. dimensions.

“This illustrates how using the placement of a single spent cartridge casing to determine shooter location is not as precise as it may seem,” the researchers write. At best, casing location can “lead to only a tentative estimate of the shooter’s location.”

The posture that most often produced the traditionally expected right-rear result was the idealized training position: the “proper” two-handed grip with arms extended and weapon uncanted and horizontal to the ground at eye level. When shots were fired from that position with the shooter stationary, ejected cases ended up in the right-rear quadrant 97 percent of the time. Even then, however, at least some rounds still landed in each of the other quadrants around the shooter.

Other positions produced more marked variances from the “norm.” For example, when a pistol was held down at a 22-degree angle and cantilevered in, as might easily occur during dynamic movement in a gunfight, less than 30 percent of expended casings landed to the right and rear of the shooter. The heaviest concentration (nearly 44 percent) ended up in the left-rear quadrant in that posture. Some 18 percent landed in the right-front.

“Changing the firearm position drastically changed the spent cartridge-casing pattern,” Lewinski says.

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Conclusions
Data from the study were exhaustively analyzed, determining ejection results according to ammunition and make and model of weapon, as well as by stance and movement. Full details were too exhaustive to be included in the Journal report, but Lewinski states that “the only consistency is the inconsistency of where spent shells landed, whatever variable was under scrutiny.

“Unlike the relatively calm and precise gun-handling of range shooting, which results often in patterns as they are expected to occur, a real-life gunfight is almost certain to be complex, rapidly unfolding, time-pressured, and life-threatening, with very different grips, stances, movements, and angles of weapon deployment brought into play,” Lewinski says.

“Each person holds and fires a gun in his or her own idiosyncratic fashion under those conditions. The variables of human dynamics are usually unknown after the fact. Yet they impact profoundly on cartridge-case placement.

“In shooting investigations, it is imperative to obtain the most accurate shooter location that can be determined from the evidence. A shooter’s location can be vital in understanding how an encounter evolved. But investigators and others attempting to reconstruct a shooting event must understand that relying solely on where a spent shell is found to determine a shooter’s firing position can be a severely flawed method.

“Hopefully the publication of this study in a peer-reviewed journal will help in burying that dangerous mythology for good.”

Besides Lewinski, the research team authoring the new report includes Force Science Advisor Dr. William Hudson; David Karwoski, formerly on the law enforcement faculty at Minnesota State University-Mankato now serving as a leadership advisor to the Iraq government; and Force Science Research Assistant Christa Redmann.

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