So, if Bob Franklin (the Baskerville scientist) moved from Indiana/USA to Devon like 25-30 years ago, how is it that he adopted the regional accent, yet somehow still (or, already?) calls the cell phone a "cell" and not a "mobile"?? 

First of all, 25 years ago (circa late 1980's), cell/mobile phones were nowhere near ubiquitous, so it's doubtful he even had one at the point that H.O.U.N.D. was running.  But apparently, not only did he have one, he became SO attached to calling it a "cell" that his subsequent 20+ years in the UK did nothing to change his name for the phone (despite the fact his American accent is completely gone). 

In America, I'm pretty sure that the first cell/mobile phones were still called mobile phones anyway, and this was in like 1992, long after Franklin had left the US. 

It's one thing if it's an American transplant who just moved to the UK 2 months ago, or even 2 years ago -- and is still stuck with "cell."  But a grown man who moved to the UK before cell phones became "cell phones," and still refers to it as such 20+ years later?  Does not compute.

Hell, I'm an American, and after watching just 6 episodes of Sherlock, I've damned-near started to refer to apartments as "flats."


It sounds trivial, but it's actually a key clue for Sherlock to deduce that Franklin was an American, THE American from H.O.U.N.D. who moved over to Devon.