New Findings On Shell Ejection Patterns Help Clear Officer on Trial for Murder

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TRUE or FALSE: Spent shell casings ejected from a semiautomatic handgun at a shooting scene can reliably tell where a shooter stood when he fired rounds.

In keeping with law enforcement lore, most officers, firearms trainers and crime scene investigators would likely say that’s true, given the operational consistency of a pistol’s ejection mechanism.

But the latest findings of the Force Science Research Center dispute that widely held belief and have the potential for changing the way many shootings are investigated.

The interaction between ammunition and a semiautomatic’s internal mechanics are important in determining the ejection pattern, of course. But the FSRC has now documented that in a deadly force encounter on the street, the ejection trajectory is far more profoundly influenced by the movements and gun positioning of the shooter.

“Depending on those variables, extracted casings can end up virtually anywhere at a shooting scene,” explains Dr. Bill Lewinski, executive director of the nonprofit FSRC. “Their final location alone will confirm virtually nothing about a shooter’s firing position unless you know how he was holding his gun and how he was moving at the time of discharge. By changing those characteristics, you can place shells all over the place.”

The Center’s new findings have already helped acquit an officer accused of murder in a controversial on-duty shooting in Arizona. The traditional ejection pattern interpretation made it appear he was lying when he described how the shooting occurred. That new scientific experiments supported his story is an important development that has international implications.

That case began when a motor officer, a former Rookie of the Year, shot and killed an attractive young mother who’d tried to pass a forged prescription at a drive-up pharmacy in a Phoenix suburb. The officer said the woman deliberately tried to ram her Camaro into him when he attempted to question her and he fired a single fatal round from his Glock-17 in defense of his life.

A grand jury no-billed the officer but a zealous prosecutor brought him to trial last June for second-degree murder and manslaughter anyway. The prosecutor maintained that the officer actually shot the woman as her car pulled away from him and, because he was not in the vehicle’s path, his life was never in jeopardy.

To support that scenario, the prosecutor introduced the principal piece of forensic evidence recovered from the scene, the spent 9mm shell casing from the officer’s sidearm. To explain its significance, the prosecutor called as an expert witness a former police department employee with extensive experience in firearms and tool marks, including the mechanical operations of semiautos.

The expended shell was found to the left front of where the officer claimed he was positioned when he fired. According to the expert, that meant he could not have been where he said he was because Glock-17s eject to the right through a side ejection port; no matter how the officer had held the gun or how he was moving when he squeezed the trigger, the Glock’s intrinsic ejection pattern could not have been changed radically enough to place a shall casing to the left front.

With the officer’s word weighed against that seemingly incriminating evidence and interpretation, it appeared he must be lying. And if he was lying about that, it would likely be assumed he was lying about everything else, including his perception that the suspect was trying to gun her car into him. If the jury failed to believe him, the officer faced a possible 24 years in prison.

“The shell casing became the underpinning of the case,” Lewinski says. “That’s why it was so important.”

Before trial, the Force Science Research Center’s Lewinski, an authority on the mental and physical dynamics of officer-involved shootings, had been brought into the case by the officer’s defense attorney.

When Lewinski met with the officer, he said at the outset that he did not want the officer to verbally describe how he was holding the gun at the time of the shooting. Instead he wanted the officer to SHOW him-to physically replicate his movements and grip.

Without prompting, the right-handed officer twisted to his left as he had in attempting to dodge the car, flared his right elbow out and canted his gun downward and to the left.

Checking out the officer’s confiscated gun from the evidence bin, Lewinski went to a range where the officer duplicated the canted angle he had demonstrated and, using the same type 9mm ammunition (Speer Gold Dot +P), fired 50 rounds on videotape.

In 40 of the shots fired-80%-the ejected casings fell to the left front, the exact quadrant where the officer’s expended shell was recovered.

Back at the Force Science Research Center’s home base at Minnesota State University-Mankato, Lewinski continued the experiments with 120 more rounds, fired under carefully controlled scientific conditions. This time he was assisted by a retired Blue Earth County (MN) deputy sheriff, Pat Gemlo, and by two FSRC technical advisors, Dr. Jeff Bumgarner, director of Minnesota State’s law enforcement program, and Dave Karwoski, a faculty member and former deputy who has seen 2.5 million shell casings ejected during his career as a firearms instructor.

This time some of the shots were fired one-handed, some two-handed and some while also making a sharp body rotation to the left. Again, the ejection patterns were consistent with the officer’s story and contradictory to the traditional expectations.

“The placement pattern was clearly established as changing with what the shooter was doing with the gun-the nature of the grip, the angle of fire, the cant of the weapon and body movement,” Lewinski says.

In court, the judge allowed Lewinski’s initial experiments to be admitted as evidence. The prosecutor agreed not to challenge those findings if the defense did not introduce the Mankato experiments into evidence.

Throughout the trial, no effort was made to refute Lewinski’s documented discoveries.

After 16 days of testimony and arguments, the case went to the jury. And after three days of deliberations, the jurors on July 9 returned their verdict: not guilty.

Had it not been for Lewinski’s testimony and for other defense experts who attacked other aspects of the prosecution’s case, “a viable defense would have been virtually impossible,” the officer’s attorney declared.

The officer, who was fired by his department soon after the shooting, has now applied to get his job back. Decisions from a municipal Merit Board and from the Arizona POST Board are pending at this writing.

*** To see DETAILED ILLUSTRATIONS of the findings that were entered into evidence from Lewinski’s shell casing experiments, go to the Force Science Research Center’s website: www.forcescience.com/visuals/shellcasing.

Meanwhile, Lewinski offers some observations on investigating officer-involved shootings that are important to keep in mind.


When investigators interviewed the Arizona officer after the shooting, he told them he held his gun “like I was taught in the academy,” suggesting a proper range-type stance with a two-hand hold and aligned sights. Given the Glock-17′s characteristics, that would have produced the disputed shell casing placement that the prosecution later relied upon in accusing the officer of lying about his shooting location.

When Lewinski, with more than two decades of experience in police behavioral psychology, interviewed the officer at length and probed deeply for details of his recollections, it became evident that in reality the officer had only three “memory fragments”-no more than mini flashes-about the shooting: he remembered the determined “escape-at-all-costs” look on the suspect’s face, he remembered the broad, racing-type tire of the Camaro coming at him , and he remembered a glimpse of the driver’s center mass as a target as he spun away.

He actually had no conscious mental recall whatever of how he held his gun.

“This is very common,” says Lewinski, who has interviewed more than 900 officers who’ve survived deadly encounters. “After an extreme confrontation, what officers truly recall are just brief chunks of what occurred. For most, details about their body positioning is lost. If asked to describe it, they’re likely to say, ‘It must have been [so and so].’

“That kind of language is a clue that indicates they don’t really remember. They’re not deliberately lying, but their mind is trying to fill in the gaps to make sense of the episode. And they often shape their ‘memory’ to match how they know they ‘should’ have shot, a la ‘like I was trained.’ This can unintentionally contaminate an officer’s story.”

For an officer to truly model an academy stance when he is scrambling to defend his life is highly unlikely. “The majority of academy training does not ingrain a response that an officer will reliably fall back on in all kinds of shooting encounters,” Lewinski explains. “When they’re fighting to survive, they may respond from a whole variety of balanced and unbalanced positions.”


Asking an officer to replicate his positions and movements will generally produce a more accurate reading of what happened than asking him to describe them, Lewinski believes.

“Under high stress, the body is so focused on reacting that the brain may generate only disjointed fragments of memory. But the principles of kinesiology and neurophysiology suggest that the body imprints a subconscious ‘muscle memory’ or what’s called a ‘muscle/joint accommodation’ that permits an officer to physically replay how he performed. This demonstration may not be perfect, but it is likely to be closer to the truth.”


Forensic observers who bring essentially a “laboratory orientation” to their after-the-fact analysis of what happened, “often can’t or don’t or won’t understand the dynamics of an actual shooting,” Lewinski asserts. “They haven’t spent a lot of time in a squad car and have no first-hand knowledge of how things happen-how absolutely crazy it can get-on the street.

“When people bring information out of the lab or the range to the street, they need to combine it with the realities of the street. They have to consider all the variables involved besides just the ideal. Otherwise they are helping create a total misunderstanding of an officer’s performance.”

As part of its on-going devotion to reality-based experiments, the Force Science Research Center is planning to continue investigating spent shell casing ejection patterns as funding becomes available, expanding its tests to include all semiautomatic handguns typically carried by law enforcement.

“We expect similar findings,” Lewinski says. “The results will have a significant impact not only police-shooting investigations but at other homicide crime scenes as well.”

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