what a load of bollocks!!! we work 5 dogs at a time... 4 will sniff and walk away, the marking dog will come along and mark! simple...And what you on about a "true mark" The dog will "mark" it simple.. either tail waging, pointing, still stance, head in and not come out, etc etc.... Plus a good marking dog will never give you a false mark(as you put it), and why should it.... Thats why there are good marking dogs and excellent ones, they never give a "false mark" as you call it...
i typed a reply and thought f**k it your obviously a lot more knowledgeable than me