There are indications that the "snitch system" certainly has it problems in the courts of the United States. Perhaps the most egregious use of pleabargaining is the case of Salvatore "the Bull" Gravano, who was allowed to go free although he himself committed nineteen murders.
In the efforts to convict crime boss John Gotti, who became known as "The Teflon Don" because of his acquittals for major crimes, the FBI taped Gotti's headquarters where he spoke of making hits on people. When the tapes contained pejorative comments about his right-hand man, Gravano, the FBI played these tapes and induced Gravano to break Omerta and testify against Gotti. In return for this testimony, Gravano went into the FBI Witness Protection Program. Later, he returned to a life of crime as a major drugdealer, along with his family, in Arizona--but not before writing a book, of course!
While there are arguments that prosecutors can get the "bigger fish" by catching the "small fish" and making a deal with them, there are certainly flaws in this system as indicated in Gravano's history. Another flaw is the fact that the "small fish" may lie in order to save themselves. There are documented cases in which these criminals have fabricated testimony that leads to the conviction of the "bigger fish" that prosecutors want. Unconscionable prosecutors do not concern themselves with this situation--even at time encouraging it--since they win their cases, make a name for themselves, and gain monetary rewards.
This pleabargaining system has not always been in place in the judicial system--at least, not to the extent that it is today. There was a time when the criminal was caught directly.