To clarify: While "shortest term" almost always applies to foreign works, my understanding is that Doyle's works are still under copyright in the UK by one of those oddball retroactive extensions. That could make the comics derived works under EU law, even though they're fully public domain in the United States. Since this site is hosted and operated in the UK, though, it makes sense to defer to Serj, who should know the local landscape better and carries the risk of any foul-ups.