Incident response and first responders
Preserving evidence does not begin only at the acquisition of data, but as early on as the physical viewing of the suspect device. There should be some kind of structured response to the suspected crime or breach in the same way as with a crime reported to the police. A person makes a call to the emergency services who then dispatch the police, fire services, and ambulance personnel, and other first responders who may then escalate the issue to the FBI or other agencies. There should also be a similar chain of command when dealing with reports that require digital investigation.
There are many sources for guidelines, best practices, and cybersecurity strategies, which you should familiarize yourself with. I'd suggest researching your local Computer Emergency Response Team (CERT) and/or Computer Security Incident Response Team (CSIRT) to begin with, such as the US-CERT (https://www.us-cert.gov/resources) and the European Union Agency for...