Dr. Pablo Carstens helps liberate about 30 victims a year
BBC Radio 4's Crossing Continents was broadcast on Thursday, 15 April, 2004 at 1100 BST.
The programme was repeated on Monday, 19 April, 2004, at 2030 BST.
Kidnapping is big business in Mexico. More money is paid in kidnap ransoms here than anywhere else in the world.
With very little trust in the police, many people turn to a private kidnap negotiator.
In Crossing Continents, Charlotte Davis is given a rare chance to witness a kidnap negotiation as it is happening.
But will the kidnappers accept a lower ransom and return the victim unharmed?
Presenter: Charlotte Davis
Producer: Sue Ellis
Editor: Maria Balinska