A person’s phone is often a source of evidence for the police during criminal investigations. People use their phones for so many different things these days that they can contain an incredible amount of information that may help during a criminal case.
In some cases, the police will ask you for your consent to unlock your phone and read your text messages or look at your social media interactions. If you do not give them consent, then they can get a search warrant. Remember that they generally cannot force you to open your phone without a warrant, and doing so may be an illegal search. But if they get a warrant, then they no longer need your consent.
Other avenues
Another thing to remember is that there are sometimes other avenues for the police to get the information they want, even if you will not give them consent to unlock your device, and they cannot get a search warrant.
Often, the issue comes down to third parties who have been voluntarily given access to your information. Maybe you share location data with your cellphone provider, so the police could get that information from your carrier, rather than from your phone. Or maybe you use social media apps to send direct messages or cloud-sharing services to back up your digital information. The police can sometimes serve a warrant to the companies that run these social media platforms or file storage systems, getting the information from them, even if they cannot get it off of your device directly.
This shows some of the complexities of gathering digital evidence in the modern age. Be sure you know about all of your criminal defense options when facing charges.

