When not to believe (your lyin’ eyes)

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An employee is charged with assault and battery based on surveillance footage recorded at the workplace. The victim is someone who the alleged perpetrator interacts with on a daily basis. The prosecution claims that the defendant “grabbed the victim by the neck” and “struck them in the ear, causing pain.” The video evidence is shown in the courtroom and appears to coincide with that description. The defendant is found guilty and receives the maximum sentence.

But there was something that seemed a bit odd about the video. The action wasn’t smooth; it was more like a stop-motion animation film. What’s the reason? Upon closer examination, it appears that this less-than-ideal playback is due to a low frame rate, or “frames per second” — commonly referred to as FPS. Could this have possibly influenced the outcome of the case?

To properly understand the video medium, we must know the essence of what we are looking at. Video is in fact a series of still images, referred to as “frames,” captured and then replayed over the same amount of time so that we perceive it to be natural motion.

Just like the stop-motion animation of a flipbook, in which we think the images are moving while fanning the pages quickly, video relies on the function of our eyes and brain to make the allowance that what we are seeing is a representation of life being recorded as it happened.

When watching television programs, for example, the most common FPS is 29.97 (the fractional nature of this frame rate is due to broadcast rules about how much time can be taken up and displayed by each program slotted for a given time). Many films use an FPS of 24, and now we are seeing some footage being recorded at 60 FPS so that it can be played back in slow motion without any perceived loss of quality.

The frame rates that are set by surveillance systems often come in much lower. It is not uncommon to see videos of 18, 15, 10 or even 5 frames per second. The problem with these lower frame rates is that when the video is played back, the footage appears staccato or “jumpy” — that is, not like natural movement.

The reason such frame rates occur usually has to do with the storage constraints of each particular system. Storing video footage, especially for extended periods of time, can become cumbersome to local hard drives and even cloud-based systems that won’t store video files for an indefinite period. Some more sophisticated systems use motion-activation so that precious storage space is only filled when something is happening near the camera.

So how might the low frame rate present an issue in our legal scenario? Depending on the charges, there is the potential for a viewer to interpret the gaps in video in a way that aligns with what they are told they are looking at. In psychology, this phenomenon is known as “confirmation bias.” It is the tendency of the human brain to want to “fill in the blanks” as confirmation of existing beliefs or theories, much in the same way as it is to perceive still frames shown in rapid succession as motion. When presented with gaps between frames, we are left to imagine what happened in a recorded incident, when we don’t, in fact, have definitive proof.

The use of language in a complaint is also of utmost importance in these scenarios, as it can suggest desired interpretations of video evidence. If we are told that an individual has “grabbed” someone “by the neck,” then we may want to interpret a hand placed on someone’s neck in that way. But if we don’t see subsequent frames with continued placement of said hand on the neck as the person being touched either reacts or is moved, we can’t say that that moment when the hand is placed on the neck is not, in fact, simply a gentle, affectionate pat.

Similarly, to say someone “struck” another “causing pain,” we would need to be able to perceive pressure, force applied, or the effects of a movement or contact. To do so, we must have enough subsequent frames of video that, when played at normal speed, show us the consequences of the physical contact that is visible.

The prevalence of digital video footage in criminal investigations continues to increase as surveillance systems become cheaper and more accessible to business owners, individuals, and all kinds of different organizations. This footage can be used to identify people or analyze specific actions performed during an incident, among other possibilities.

However, it is crucial that legal professionals understand that not all videos are created equal. When attempting to verify culpability based on allegations made, we must assess the different components that make up video footage. In particular, the frame rate or frames per second can greatly affect our perceptions and interpretations of what we are seeing. When the gaps between frames are large, video evidence that is purported to show specifically designated actions must be questioned and analyzed thoroughly.

But this is not the only parameter that could come into play. Exposure and contrast that affect visibility and clarity, motion blur, video resolution, and a host of other parameters could potentially affect what we can and can’t see in video evidence.

When attempting to verify culpability based on allegations made, we must assess all the different components that make up video footage. To not do so when lives hang in balance would be a grave injustice.

Daniel Lawren is a CPCS Approved Video Expert with Lucidity Video Solutions. He can be contacted at [email protected].