The term "person of interest" is sometimes used by police and prosecutors in criminal investigations. Doing so is especially common if there is any level of media reporting, even if it's just your local newspaper coverage. If you've been described as a so-called person of interest, it's a good idea to learn what that means and how to address the situation.
Definition
The usage of the term has increased over the last couple of decades. Police use it because it's considered less offensive than calling someone a suspect. As police forces have been exposed to more defamation, libel, slander, and civil rights complaints for falsely accusing people of crimes, this term has emerged. The idea is basically to insulate the police from civil lawsuits for making accusations.
It's Impact
For you, the problem is simple. Any interest the police take in anyone runs the risk of being bad news for that person and the folks around them.
Bear in mind that innocent people do end up being investigated. And yes, innocent people end up in jail. You don't want to be a suspect, person of interest, or even a witness if you can possibly avoid it. The police are good at finding things to charge, and they'll charge people with process crimes like lying, tampering, or obstruction even if they can't produce a crime of any other sort.
What Can You Do?
From the instant the cops take an interest in you, contact a criminal law attorney. Even if a police officer says they just need you as a witness, lawyer up. When the police come to your house and ask if they can come in, decline. Tell them they can enter when they can produce a warrant signed by a judge.
If you are stuck dealing with the cops without counsel, inform them you want a criminal law attorney present. Do not discuss anything with the police until a lawyer shows up. They might talk at you, but refuse to engage with them unless a lawyer is there.
Should you slip up and start chatting, tell the cops clearly, "I am invoking my right to remain silent." Do this even if a conversation got rolling after something simple, such as the officer asking you if you want a cup of coffee. It's better to sound like a broken record than to end up saying something that could be used against you in court at a later time.