To be convicted of accessory after the fact in Tennessee, the State must prove that you knew or had reasonable grounds to believe someone committed a felony and that you acted with the intent to hinder the arrest or prosecution of the defendant. If you hide, help or warn someone in some way with the intent to help them avoid prosecution you could face an accessory after the fact charge.
Police may believe that you were attempting to help someone elude capture by telling them they had an outstanding warrant. But, simply informing someone that the police are looking for them is not, in itself, committing accessory after the fact. For example, if you were trying to encourage the person to turn themselves in, you were not acting with the intent to hamper their prosecution.