Several ways to dodge the statute of limitations, if that's what you're referring to.

First, not all charges have the same length of limitation. Some have no limit at all.

Second, when one charge builds or is aggravated due to another, it's limits can be lengthened. For instance, let's say a particular charge (Charge A) carried a one year limitation on it. If you investigated someone else for Charge B for two years and then found out that Charge A coerced them to commit Charge B or that Charge A was a direct precursor to Charge B, Charge A can have an extended statute of limitations (or a different charge that carries a longer limit, like Conspiracy or Racketeering charges).