The camera lens may seem like an objective eye _ but it's the video playback where things can get tricky.
A new study finds that when viewers watched a video of a violent act, they were far more likely to ascribe ill intent to the person who did it if the video was played in slow motion.
The findings, described in the Proceedings of the National Academy of Sciences, show how differing presentations of the same video can significantly affect a viewer's sense of events. In the courtroom, the authors say, this could have serious implications for the decisions by juries and the fates of defendants.
With businesses' security cameras, police officers' body cameras and ubiquitous smartphone cameras filming the world every day, violent acts are increasingly being caught on video and ending up in courtrooms. Such footage can be crucial evidence when a victim's or witness testimony isn't sufficient to persuade a jury.
"Because video affords repeated viewings, it can augment the limits of human attention, visual processing and memory," the study authors wrote. "Because video can be slowed down, it also provides the ostensible benefit of giving people 'a better look' at real-time events that happened quickly or in a chaotic environment."
But while video might seem objective compared with an individual's recollection, humans still have to interpret what they see. And that interpretation could have life-or-death consequences. The study authors point to a 2009 murder case that eventually made its way to the Supreme Court of Pennsylvania.
The prosecutors originally showed jurors surveillance video of John Lewis fatally shooting a Philadelphia police officer during an armed robbery, presenting the footage in slow motion. Ultimately, the jurors found that the shooting was premeditated (making it first-degree murder), not reflexive (which would make it second-degree murder). This opened the possibility for death by lethal injection instead of life in prison.
The defense appealed, pointing out that the slowed video "artificially stretched the relevant time period, creating a 'false impression of premeditation,' " the study authors wrote.
The prosecutors, however, argued that the jury saw both the regular-speed video as well as the slow-motion version and were made aware of that actual time span, in which Lewis shot the officer about two seconds after seeing him at the door. The Supreme Court sided with the trial court, finding that the slow-motion footage was "more probative than prejudicial."
Intuitively, that court decision may make sense; after all, the jurors were given all the facts of the case. But the study authors wondered whether the defense had a point, that slowing the tape makes it seem as though the suspect had more time _ perhaps enough to plan out the act.
"Although timing will be irrelevant or uncontroversial in some behavioral sequences submitted for the court's inspection," the authors said, "the question of whether an actor had a 'long enough' window to assess and prepare to inflict the harm is likely to be central in many disputes."
To investigate this question, the researchers set up a series of experiments. In the first study, participants were asked to act like jurors in a criminal trial. They were shown real surveillance video of five seconds of an attempted robbery in which the assailant shoots a store clerk. There was a digital display showing the actual elapsed time. Some of the participants watched the video at regular speed, and the others watched it in slow motion, 2.25 times slower than reality, which is also about the same slow-down rate for the video that jurors saw in the Lewis trial.
After watching either version, they were asked whether the assailant shot the gun "with the intention to kill the victim," as well as how willful, deliberate and premeditated the action was. They also were asked how much time they felt the shooter had to assess the situation.
The researchers found that 77.3 percent of those who saw the regular video thought the action was intentional and that 86.2 percent of those who saw the slow-motion video felt that way. And when they ran simulations of 1,000 12-person juries based on their data, 39 juries whose members saw the regular-speed video unanimously agreed that the assailant shot with the intention to kill. In sharp contrast, 150 juries who saw the slow-motion video unanimously judged that the attacker had intended to kill the victim _ nearly four times as many.
The scientists wondered whether this time-distortion bias had the same effect in situations that didn't involve criminal actions. So in a second experiment, they had participants watch a video of an NFL football player in the act of a prohibited helmet-on-helmet tackle; the effect held. The slow-motion viewers were more likely to think the player hit his helmet against his opponent's on purpose.
In a third experiment, viewers were reminded, over and over again, that three seconds had passed based on the digital time stamp. This seemed to help reduce some bias seen in the first two experiments, but not all of it.
"Although making clock time salient successfully decreased the bias in estimates of clock time, it did not significantly affect the difference in estimates of the time it felt like the shooter had," the study authors explained. The slow-motion viewers still felt that the shooter had more time to assess the situation before pulling the trigger.
In the fourth set of experiments, the researchers also had some participants see the regular-speed film, followed by the slow-speed version. Although seeing both speeds seemed to mitigate the bias somewhat, it didn't fully correct the problem, the authors found.
"Compared with simulated juries who saw only the regular-speed video, the odds of a unanimous first-degree murder verdict were 3.42-fold higher among juries who saw only the slow version, and 1.55-fold higher among juries who saw both versions," the study authors wrote. "These results demonstrate that giving viewers the opportunity to view both speeds reduces the intentionality bias, but does not eliminate it."
This doesn't mean that slow-motion video shouldn't be used in court, the authors emphasized, but it does mean that their potential benefit has to be weighed against the possible costs.
"The present investigation cannot determine whether slow-motion replay makes viewers more or less accurate in judging premeditation in these situations, but it does demonstrate that slow motion can systematically increase perceptions of premeditation itself," they wrote.
The authors emphasized that this is early research and that a lot more has to be done to try and understand the effect of slowed-down video in light of other confounding factors. Does the viewing order matter? Does the number of times the video is seen affect perception? Perhaps the speed of playback matters. Perhaps if you slow down the video even more, it will cease to affect people's perception of time.
"At a certain point of 'superslow motion,' actors may appear to be moving at nonhumanly slow speeds and seem less likely to possess any mental states, including intentions," the study authors hypothesized.
In any case, they concluded, "it seems imperative that an empirical understanding of the factors that contribute to assessments of intent inform the life-or-death decisions that are currently based, in part, on the intuitions of lawmakers and their tacit assumptions about the objectivity of human perception."
