You can seize and keep the phone, though this won’t sit well with the civilian who owns the phone and likely depends on it. The best alternative: carefully documenting each action, you need to perform a forensic collection of the phone’s data. Only after obtaining the evidence should you feel comfortable erasing the contraband video and giving the phone back to the witness.
5. How do you preserve video evidence without also collecting civilians’ private data?
OK, so we've established that a properly forensic collection is needed. Can you pick and choose what data you obtain?
You can, but only to a point. With most mobile forensic extraction tools, you can obtain a certain type of data -- say, video -- and not get other data, but you can’t pick and choose which videos or images or text messages to collect. Once the relevant data is extracted, you can (and should) pick which ones show up in your report.
It’s important to remember that the forensic collection actually protects a civilian’s private information. Your scrolling through their device is no less intrusive than the forensic collection, and carries with it additional liability if you happen to erase something important.
6. What if you find evidence of other criminal activity?
It happens a lot: you’re looking for evidence of drug dealing but find child pornography instead (or in addition to). What do you do?
It depends on the circumstances of your search. With consent, a search incident to arrest in many (but not all) states, exigent circumstances, or plain view, your actions will likely be covered. However, if you have a search warrant for one type of crime but find evidence of another, it’s often considered a best practice to stop immediately until you can get another warrant.
7. How many copies or angles of video do you need?
Conceivably you need as many angles as you can get. One person’s perspective may provide context that another’s couldn’t, simply because of how they were positioned while filming. Bystanders walk in front of cameras, image quality can differ.
Even so, organizing multiple videos can be challenging. But while simply viewing the videos and documenting what you see may be more convenient, it still can’t be considered a full evidentiary collection.
8. What if it's another BART situation?
Bystander video of any potential police misconduct has to be handled delicately. In most states it’s a citizen’s right to photograph and record police interactions with civilians, so unless you have probable cause to believe the phone contains evidence of a crime, seizing their phones without consent is illegal.
Yet, cell phone video was critical in the case against Johannes Mehserle, who was convicted only of involuntary manslaughter after cell phone videos backed up his account of events. If you have PC, seize the phone, preserve it, and get a warrant to search it later -- especially if it’s possible a police officer committed a crime.
9. Are there other forms of evidence you can use?
You may not need civilians’ cell phone videos if you can collect corroborative evidence from business or public surveillance cameras. Make sure you have access to a professional who can properly recover and analyze this kind of evidence.
Forensic collection of cell phone evidence is a matter of training, and it can be challenging to train lots of people in an agency to this task. However, lawyers and judges are becoming more educated on digital evidence. Whether you’re getting data from a suspect, victim or witness, have the right policies and standard operating procedures in place; train as many people as needed to support those procedures; and stay in touch with your prosecutor on the latest legal precedents.