From what I've seen on how these gangs/cartels operate, which I believe was actually shown on one of those banged up abroad shows is that they work like so:
- They are first lured by somebody quite impressionable, say a good looking guy, who speaks their language and befriends them.
- They are invited on a holiday, with or without the information that they are going to be asked to carry something 'small' back with them. While being given an all expenses paid holiday and some money.
- They are checked into a hotel and their passports are taken by the gang, so they can't leave. In the particular case I saw, they were basically held hostage in a hotel room. In another they were given freedom to go do what they wanted, but still didn't have their passport or ticket home.
- The gang turn up with loaded suitcases, plane tickets and their passports. They then take them to the airport where they are forced to board the flight and are waiting outside incase they try and do a runner or alert anyone.
I think what actually happens is that there are then two different aspects in play. The first is the intimidation of the gang in the airport, that they may kill you or something if you don't do as instructed. The second is that now you are in the airport, even if you try and alert somebody, you may already been seen as a drug smuggler as you are trying to board a flight with kilos of drugs. So at that stage, these people really don't have much choice but to go along with it.
So ultimately its not impossible to see how somebody was forced into it. However, the right thing to do would be to alert somebody. Of course though you can't dismiss the fact that at some stage the mules are somewhat complicit in what they are doing. You would have to be seriously naive or have a handicap to believe that somebody is going to give you a free exotic holiday and cash for nothing, especially when these kind of smuggling cases are widely publicised these days.