This "fault"-based ground for divorce goes hand-in-hand with a finding of "guilty" in a criminal matter, followed by a sentence of five years or more in prison. It is not the amount of time that is actually served, but rather what the sentence is that matters. Proving this grounds for a fault divorce is generally straightforward.
Interestingly, if after a divorce, the imprisoned spouse is pardoned for his or her crime(s), the marriage is not restored.
As with most grounds for divorce, there is no advantage over "no fault" divorce. Proving that a spouse has been sentenced to five or more years in prison is slightly more difficult than meeting the evidentiary burden required in a "no fault" divorce (only that one spouse is able to tell the court that his or her marriage is irretrievably broken down with no chance of reconciliation).