Case Studies: How Force Science Analysts Helped Accused Officers

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Time-and-motion concepts researched and taught by the Force Science Institute are most often used to unravel the complexities of officer-involved shootings. But 2 recent cases demonstrate the value of these principles in assessing other types of law enforcement encounters as well.

In Nevada and British Columbia this summer, graduates of the certification course in Force Science Analysis, where human behavior studies are explored in depth, have used that training to help officers accused of wrongdoing in pursuit and physical control situations.

In one case an officer was saved from a possible prison term on felony charges. In the other, an officer’s controversial pre-emptive actions in stopping an attack before it started were vindicated, clearing him and 2 backups in a citizen’s “excessive force” complaint case.


The chase case, which eventually involved Force Science Analyst Jeff Martin as an expert witness, began about 2220 hours on a Wednesday in May, 2010, in a commercial/industrial section of northeast Las Vegas.

Behind the wheel of an old black Honda Civic, a suspect later identified as 26-year-old meth abuser Ivan Carrillo was driving so erratically—creeping along at 12-15 mph, swerving across lanes, stopping suddenly in front of another motorist—that a citizen phoned 911 to report him. Among responding officers were Andrew Ubbens, 26, and Aron Carpenter, 29, in marked units of the Las Vegas Metropolitan PD.

Earlier in the day, investigation would show, Carrillo had been involved in a domestic dispute with his girlfriend and mother of his daughter, who told him he “scared her” and said she didn’t want to see him anymore. He argued that life would not be worth living without her. In an interview with Force Science News, Martin speculated that Carrillo, high on drugs, may have deliberately sought to attract police with his bad driving, with a suicide-by-cop-type plan to make it look like they caused his death during a pursuit.

With Ubbens and Carpenter behind him, Carrillo now took off, cranking the aged Honda up to 60 mph while weaving through traffic. The officers gave chase, but a sergeant heading toward the area quickly called off the pursuit. The officers maintained later that they eased off active pursuit but “continued to follow” at normal speeds without emergency lights or sirens, anticipating an inevitable accident and thinking they should be close by to help anyone injured.

After Carrillo locked brakes and skidded sideways through an intersection, after he drove north in southbound lanes, after he successfully drove out of a PIT maneuver by Ubbens, after he slowed as if to stop then speeded up again, the accident occurred in a matter of mere minutes.

As Carrillo’s path crossed into the city of North Las Vegas, Carpenter was “allowing him to drive away,” the officer later testified. Suddenly Carrillo, driving in an adjacent lane, decelerated and cut sharply in front of him. The officer said he stomped on his brake pedal and jerked the steering wheel, trying to avoid him. He felt a bumping sensation and heard a grinding sound that seemed to indicate he’d struck the left rear of the suspect’s Honda.

Carrillo steered back into his own lane, then accelerated and spun the Honda across multiple traffic lanes and into oncoming traffic. The resulting pileup wrecked 4 vehicles and left a woman motorist seriously injured. Carrillo was killed.

During a departmental investigation, the sergeant averred that he had 3 times ordered “all units” to discontinue pursuing and that Ubbens and Carpenter had consistently defied him. The theory developed that Carpenter, while traveling at high speed in continued pursuit, was driving too close to the suspect and that contact between the cars caused Carrillo to lose control and veer to his death. Carpenter insisted that he was driving at legal speed, that he made no intentional collision with the suspect’s vehicle, and that he was not in active pursuit at the time of the fatal crash.

Nonetheless, the PD recommended to the county District Attorney’s Office that both officers be charged criminally. In September 2010, Ubbens was charged with misdemeanor reckless driving. For Carpenter, more serious charges resulted: 2 counts of felony reckless driving. Found guilty, he could face 6 years’ incarceration and $5,000 in fines on each count.

Last January, Ubbens pleaded no contest to failure to use due care, a misdemeanor. He was ordered to pay a $500 fine and perform 50 hours of community service.

Carpenter refused to cop a plea. He was fired and went to trial.

Martin was the final witness called in his defense during a week-long jury trial in Clark County District Court last July. An expert in pursuit policy and tactics, Martin is himself a police attorney in California and a former municipal officer there with 28 years’ LE experience. He received his Force Science Analysis certification in 2008.

Much of Martin’s expert witness testimony under questioning by defense attorney Bret Whipple concerned the “fluid and dynamic” situation Carpenter faced during the final 10 seconds leading up to the crash.

While the prosecution claimed that reckless driving by Carpenter had contributed to the fatal accident, the defense raised doubts that contact between the cars had even happened, let alone been the cause of Carrillo veering to his death. What Carpenter interpreted initially as an impact could have been the sensation and sound generated by the thumping effect of the officer’s anti-lock braking system forcefully engaging. Indeed, there was no forensic evidence that conclusively established that collision actually occurred.

Be that as it may, Martin testified that perception and reaction time, not recklessness, was a key factor in this rapidly evolving and unusual event. Even traveling at or near legal speed, as Carpenter claimed he was, he would have been thrown severely behind the reactionary curve by Carrillo’s sudden swerve in front of him, Martin explained.

Drawing on a classic model used in the certification course, he described for the jury the 3 steps of reaction:
  1.  Identification of the stimulus. If you’re primed to see something, you can react faster, Martin explained. But something unexpected—Carrillo’s abruptly decelerating and swerving into Carpenter’s path, in this case—delays recognition. Carpenter’s attentional focus at the time this happened—had he been glancing down at his dashboard, for example—could have delayed awareness of the problem even more.
  2. Selection of a response. Force Science has measured lag time incurred even by having to make simple “go/no go” decisions. But that time is extended, Martin explained, when more options are available and you have to decide among several which to choose, the situation Carpenter faced in trying to determine the best defensive driving maneuver for avoiding Carrillo’s car.
  3. Initiation of response. Executing the physical maneuvers to follow through on the choice that’s made adds yet more time.

Martin says, “What I hoped to convey to the jury was that any contact between the squad car and the suspect’s Honda was the result of an inevitable lag in stopping time rather than a deliberate or reckless impact. And at worst, any contact was no more than an insignificant glancing brush. It was not decisive in Carrillo’s controlling his vehicle and was not Carpenter’s fault.”

In his opinion, Martin testified, Carpenter had acted reasonably throughout the engagement and was “driving with due regard,” in compliance with the department’s pursuit policy and not in rogue defiance of the sergeant’s orders.

As Whipple put it in his summation, Carpenter “was an officer trying to do his job to the best of his ability. He wasn’t trying to hurt anyone.”

The jurors were out for less than an hour. Their verdict: not guilty by a vote of 12-0.

Tears welled up in Carpenter’s eyes after the verdict was read. “The nightmare I’ve had to live for the last year and 2 months has finally come to an end,” he told a reporter for the Las Vegas Review-Journal. “I stood up for the truth. I had no intention of being that close to him.”

Through arbitration, he now hopes to get his job back.


The Canadian case, in which Force Science Analyst Steven Ing played a key role, also started with what appeared to be an impaired driver.

After midnight one morning, about 2 months before the Las Vegas pursuit, an officer on patrol in Victoria, BC, pulled over a van whose male driver appeared to be steering erratically, weaving and making wide turns. The neighborhood being “rather rough,” 2 backup officers quickly responded.

As the primary and 1 backup approached the vehicle toward the passenger side, they heard “a weird banging noise from inside.” Then the van’s panel door slammed open and the driver leaped out, highly agitated.

They ordered him back inside, but he refused to cooperate. He continued his resistance despite repeated commands and seemed to be moving toward what the officers thought would be physical aggression.

The primary officer went hands-on and with the help of the backups and well-placed knee strikes, took the subject down and handcuffed him. The driver suffered some abrasions in the process.

As it turned out, he wasn’t drunk or high, just a mental patient off his meds. His van had some mechanical problems that affected the steering. After he passed roadside sobriety tests, the officers dusted him off and sent him home.

The subject waited nearly 9 months before filing a citizen’s complaint. Besides challenging the legality of the stop, he claimed the officers had no grounds for taking him to the ground and used excessive force in the process, causing his injury.

The flow chart for complaints “looks something like a nuclear science diagram,” Ing says, but eventually the matter landed on his desk. With a law degree and 23 years’ LE experience, much of it in uniform assignments, Ing is now an inspector who heads the department’s Executive Services & Professional Standards section. Among his responsibilities is assessing evidence gathered during internal investigations and rendering decisions on the merits of public complaints.

In this case, the primary officer stated that he initiated the takedown on the basis of certain “pre-assaultive cues” that convinced him that the complainant was preparing to physically attack him. These included, in addition to verbal hostility, the driver “squaring off in a combat stance,” clenching his hands into fists, exhibiting a “1,000-yard stare,” and displaying “resistive tension” during their dialogue beside the van. The backup officers confirmed that such indicators had been present.

“It was a good list,” Ing says, and from his own street experience and martial arts background, he agreed that such cues can be valid predictors of pending aggression. He believed the officers’ force was justified.

The problem was that his decision was subject to review by an external independent civilian oversight body. If that group disagreed with his finding, the case would then go before a retired judge for further assessment.

In British Columbia, Ing explains, civilian overseers (as well as the media and activist lawyers) had previously “expressed concerns over the use of ‘pre-assaultive signs’ to justify use of force by police.” Questions had been raised about “how you can predict what someone is going to do,” and the sentiment among some reviewers (“official and unofficial”) seemed to be that “an officer had to take a punch first” before reacting.

“I needed to explain to people who had never been in physical combat why officers sometimes need to use pre-emptive force and why it can be justified at times when a subject technically hasn’t ‘done anything’ yet,” he says.

Shortly before becoming involved in the case, Ing had graduated from the Force Science certification course. He decided to frame the “cues” issue in the context of “a concept spelled out in scientific detail” in that training.

As part of a 12-page report he submitted to the civilian reviewers, he explained “the principle that action will always be faster than reaction.” That means, he wrote, that in a force confrontation an attacker who acts spontaneously “will always be able to initiate an attack before an officer can react to it.”

Police officers “in the lawful execution of their duties are not expected to suffer a physical assault before exercising their authority to arrest or to use force to defend against an assault,” Ing maintained. Consequently, an officer observing and then reasonably “using ‘pre-assaultive’ cues to help determine whether or not an assault is imminent…is a valid practice that does not undermine the officer’s credibility.”

“Force Science helped me understand the scientific basis behind this and helped me learn how to frame the concept in language ordinary people could understand,” Ing says.

In July, he learned that this training paid off. “The civilian oversight body held that my findings were reasonable,” he reports, “and no further action was taken against the involved officers.”

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