If there's a fear that the person might end up taking a case against the company in the future, then it would be prudent. A lot there will depend on the person and the nature of the condition.
We had a case a number of years back with an ongoing medical issue. After advice, we sought such a cert and had the person attend a company appointed doctor (our policies explicitly allowed for such scenarios). In that case the doctor stated the working environment would be detrimental to their recovery, and so they were not fit to return to work.
You'll need to tread very carefully though, and your options now will very much depend on how well you're covered your bases in employment contracts.