Video speed, frame rate, slow motion and interpretation!

Many people within the Forensic Video community have been discussing this recently published study on ‘slo-mo’ playback in Courts.

Slow Motion Increases Perceived Intent

It made the international news and I tweeted the story, stating that there was actually more to this than just slow motion footage..


So, what is the rest of the story…?

The study suggests that by seeing actions at a speed that do not match reality, jurors may interpret the actions of people incorrectly.

What should be discussed though, as a result of this study, is why jury’s are being left to interpret the video evidence by themselves in the first place?

It’s not just the times where a video has been slowed down on purpose. There are more problems likely with all the footage played back where the speed was unknowingly incorrect.

These are often too fast, rather than too slow. The other scenario is when video is played back at a regular, constant rate, rather than the variable rate that was used during the recording.

During playback, especially in a courtroom environment, these discrepancies are hard to spot, but they can change the meaning of the video, resulting in the wrong interpretation.

How can a video be presented in a court that was unknowingly incorrect?

CCTV and mobile video is extremely easy to process incorrectly. It’s also quick. What do you think happens to most?

Is it analyzed and processed in a forensic manner? Without the correct analysis, issues such as variable frame rate, missing and duplicated frames and frame rate averaging can be missed. If a video is processed incorrectly, because it has not been analyzed properly, and then the wrong presentation format used, even a very slight change in speed and motion may change a persons interpretation of events captured.

Do the Courts allow for the correct video to be presented by a Forensic Video Expert, in the format and medium decided by them?

Court cannot play CCTV

I  have talked, and written, about many of these issues before. The key point though is that if a video is not analyzed and presented correctly, it could be interpreted incorrectly.

I have not produced ‘slow motion’ footage for some time. I prefer to present the video at a speed that I have identified to be as near to reality as possible (sometimes not as easy as it sounds). When this can not be ascertained, then that fact is documented. When certain elements of an incident are required to be analyzed individually, I prefer a frame by frame approach, rather than an automated ‘slo-mo’.

When timing and frame duration are a key element, these also must be forensically examined to ensure the facts are presented.


If we continue to allow video that has not been analyzed correctly, and processed incorrectly, into courtrooms – what do you expect is going to happen? Do we carry on allowing untrained persons to dictate a presentation medium unsuitable for the evidence?

It’s not just a simple case of setting guidelines for using slo-mo footage. It has to be understood that video should be acquired, analyzed and presented correctly to start with. Only then can we begin to mitigate against incorrect interpretation.

By Spreadys Posted in EEPIP

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