Sergeant1107 wrote on Dec 19^th, 2009 at 12:52am:

Hiring a private detective to follow your partner does not fit any legal definition of stalking.  It doesn't even fit the definition of stalking to which Miss Sack included a link.

True, true.  If it were the case, then by definition ANY private investigator could be classified (and charged I presume) as a 'professional' stalker!  That's why private investigators require training and licensing/certification in order for them to do what they do, especially in surveillance of individuals.