Interpol?  Interpol acts like a liaison between different country's police.  They don't really investigate anything.  They just get information on criminals from other investigating bodies and send that information to others.  You'd have to go to your local police, tell them about Sovu (Or whoever) and then that police would contact interpol and tell them about their active investigation.  At which point, when he is picked up in Swaziland or whatever, Interpol is notified and they hand him over to your local police.

You might be watching too many TV shows of Interpol flying around making arrests.  

From Interpol's FAQ:  

"How do I report a crime to INTERPOL?"

"If you have information about a crime being planned or that has been committed, or if you are the victim of a crime, you should report this to your local or national police authorities. They can then access the appropriate INTERPOL channels if required. The INTERPOL General Secretariat can deal only with information provided by the appropriate law enforcement agencies, not members of the public."