Keep suspects in the dark
When arresting or detaining a subject, think about what kind of information he or she will be exposed to. If you're placing suspects in your squad car, don't give them the opportunity to learn about the full nature of the investigation. Here are some things to keep in mind:
If you have a computer or radio in your cruiser (as I'm sure most of us do), turn the computer monitor off and turn off or mute the radio as well. This will prevent the suspect from gathering information on the process and current stage of the investigation.
Don't give the subject the chance to know how you and other cops at the scene are operating — don't let them hear our radio traffic and prevent them from viewing updated call history on your computer screen.
These communications tools there here to help us, not help the suspect or allow them to interfere with our investigation.