Capetonian,
Don't know about your neck of the woods, but in the UK the truth is an absolute defence against defamation (both libel and slander) and trumps any circumstances.
For a pursuer to win a defamation action they must first prove that the written or spoken word is false (and the onus is on the pursuer). If they do prove it to be false, they still have plenty of other hurdles to get over as well. If they cannot prove it is false, they lose.
JS is one hundred percent correct - it is never defamatory to speak/write the truth. Just make sure you can prove it is true, in case they come at you with the heavy duty lawyer squad.