INFORMANTS HAVE PLAYED A USEFUL ROLE IN APPREHENDING AND CONVICTING CRIMINALS BECAUSE THE INFORMATION THEY SUPPLY OFTEN PROVIDES THE NECESSARY PROBABLE CAUSE FOR ARREST OR OBTAINING A SEARCH WARRANT. A TWO-PRONG TEST IS APPLIED TO DETERMINE WHETHER THE INFORMATION AN INFORMANT PROVIDES IS SUFFICIENT TO ESTABLISH PROBABLE CAUSE. FIRST, THE OFFICER MUST HAVE SOME KNOWLEDGE OF THE UNDERLYING CIRCUMSTANCES FROM WHICH THE INFORMANT CONCLUDED THAT A CRIME HAD BEEN COMMITTED. SECOND, THE OFFICER MUST HAVE REASON TO BELIEVE THE INFORMANT IS CREDIBLE, OR HIS INFORMATION RELIABLE. THE TEST IS PRIMARILY APPLICABLE IN SITUATIONS WHERE THE INFORMANT IS HIMSELF A PART OF THE CRIMINAL ELEMENT. BECAUSE THE COURT RECOGNIZES A GENERAL RULE KNOWN AS THE PRIVILEGE OF NONDISCLOSURE, INFORMATION SUPPLIED BY INFORMANTS CAN BE USED TO UPHOLD PROBABLE CAUSE WITHOUT THE INFORMANT TAKING THE STAND TO TESTIFY, ALTHOUGH THE INTERESTS THAT ARE PROTECTED BY NONDISCLOSURE MUST BE CONSTITUTIONAL AND WEIGHED AGAINST THE RIGHTS OF CRIMINAL DEFENDANTS. HOWEVER, IF AN INFORMANT TAKES THE STAND HE IS NOT PROTECTED BY THE NONDISCLOSURE PRIVILEGE AND MAY BE QUESTIONED REGARDING HIS REASON FOR TESTIFYING, HIS INTEREST IN THE CASE OR ITS OUTCOME, AND HIS PARTICULAR PREJUDICES AGAINST THE DEFENDANTS. INFORMANTS MAY ALSO BE QUERIED ON THEIR TRUE NAME, PLACE OF RESIDENCE, AND WHETHER THEY ARE RECEIVING ANY COMPENSATION FROM THE PROSECUTION. FEDERAL REVENUE STATUTES PROVIDE INFORMER'S FEES FOR WITNESSES TESTIFYING OR PROVIDING INFORMATION LEADING TO A CONVICTION. LAW ENFORCEMENT AGENCIES HAVE ALSO BEEN KNOWN TO REWARD INFORMANTS. NO DIFFERENTIATION IS MADE BETWEEN INFORMANTS IN CIVIL AS OPPOSED TO CRIMINAL CASES. REFERENCES ARE FOOTNOTED. (KBL)