You're correct, Oz. "Hanged" is more proper-speak, "hung" more colloquial (a good way to write in this milieu IMO).
According to Merriam-Webster's:
For both transitive and intransitive senses 1b the past and past participle hung, as well as hanged, is standard. Hanged is most appropriate for official executions <he was to be hanged, cut down whilst still alive … and his bowels torn out — Louis Allen> but hung is also used <gave orders that she should be hung — Peter Quennell>. Hung is more appropriate for less formal hangings <by morning I'll be hung in effigy — Ronald Reagan>.
And a further
apropos comment for the anonymous internet pedant posting as Kibitzer:
If you make a point of observing the distinction [between hanged and hung] in your writing you will not thereby become a better writer, but you will spare yourself the annoyance of being corrected for having done something that is not wrong.