Why do people also say I knew he or she was headed for trouble.?

Question

When it turn out they were not, but just travel the wrong path.

Answer 1

Because some people can see it coming by the actions of the person in trouble.  Let's say "Joe" was an average student in school, got detention once in a while for talking or being late, nothing major.  Then he meets new friends, and soon he is getting suspended for things like vandalism, getting into fights, etc.  He is also caught drinking (he's only 16) which he never did before, his new friends all have criminal records, he starts staying out all night, etc.  Then one day he is arrested for being in the getaway car when his friends robbed a store.

People around him saw the change in him, saw it was for the worse, and knew one day he would really end up in big trouble.

Answer 2

the people who use that phrase always want to be right and prove they could tell. Some of us do travel down the wrong path and some may use the phrase b/c they have been down that same wrong path before.  

Answer 3

You are splitting fine hairs. Semantics aside, it's an easy term to get.