Ricky tells McClane earlier in the film that he bets his badge number - 6991 every week in the lotto. The terrorist takes the badge from Ricky's dead body pretending to be a cop but McClane notices the badge number in the elevator, thus realising something is wrong.
He was also suspicious after asking them if they know the lottery numbers and the germans didn't. In the van at the beginning of the film all the 'american' cops knew the numbers cause they play regularly.
1) He knew Ricky's badge number, and saw the one guy was wearing it.
2) Called the elevator a lift.
3) Dogs and cats, instead cats and dogs.
4) You would have a better chance of winning the lottery, than finding a New York City Police Officer who doesn't play the lottery, let alone 3 in one elevator.
Thats because it was a lift. Elevator is what you have in a mall. Skyscrapers have lifts. The word elevator comes from a company by the same name by the way. Its one of the very rare examples of trademark going into public domain.
the lotto thing is not a nationality thing. It's a cop thing. Cops are dumb enough to take the job, dumb enough to not live comfortably on the pay, and dumb enough to think they'll win the lotto and save every bad decision they've ever made in their lives.
This is why I love this film. A seemingly innocent smalltalk scene is tied in. The smalltalk scene alone works enough, as it just exists to show the personalities in the van. But they also gave it a bigger pay off.
I have a question regarding this scene. What's with it taking John like 5 shots with his gun at point blank range for the bullets to finally hit Otto's head 10 seconds later? That makes no sense to me and never has. He shoots him in the head several times and then after shooting it like 5 times his head is blown off. Weird.
That scene was out there. Loads of Americans mix up expressions. And does McClaine seem like a guy who realizes that "lift" isn't used anywhere in North America? It's stupid anyway that a German guy who speaks English so well would mess up like that. The only things to give it away were the badge, the weird accent and maybe cop instinct.
To be fair I think it's more an accumulation of things, so that mixing up expressions, saying "lift," and not playing the lottery gradually increased John's suspicions until the badge number confirmed beyond doubt that these were imposters.
I doubt it was just John thinking to himself "my god, this man said 'dogs and cats,' clearly he is evil and shall soon meet his demise."
Yep. Plus remember he's been in situations before where things just didn't sit well with him and his Spider-sense began tingling, like in the first film when he meets Hans in that hallway, or in the second film when he notices the magazines were tagged with red and blue tape and eventually figured out the "good guys" weren't so good because they were using blanks against the terrorists.
It doesn't take a bad fart in a crowded elevator for John McClane to figure out there's a rotten egg about.