The Case that set the Precedent
In 1983 the United States Supreme Court issued a ruling in Illinois v. Gates, 462 U.S. 213 (1983) defining what constitutes probable cause. To better understand the following United States Supreme Court decision defining the rule of probable cause, here are some applicable facts. In the case of Illinois v. Gates, an anonymous letter was submitted to the Gateses' local police station informing the police that Lance and Susan Gates were selling illegal drugs. The letter went into detail regarding where the Gateses lived, where they kept the drugs and how they received the drugs. The letter contained exact details regarding when the Gateses were buying their next round of drugs and how the drugs would be transported to their home. The local police contacted the Drug Enforcement Agents (DEA) and put them on notice of the Gateses' alleged conduct. The local police and the DEA followed the Gateses' trail. All the information contained in the anonymous letter proved accurate.
What Constitutes Probable Cause?
The case of Illinois v. Gates brought about the question of what constitutes probable cause. In other words, was the anonymous letter enough information for a magistrate to issue a search warrant of the Gateses' home and automobile? The United States Supreme Court stated the correct standard for determining whether there is probable cause is to consider the totality of the circumstances. "Under the 'totality of the circumstances' analysis, corroboration by details of an informant's tip by independent police work is of significant value." Illinois v. Gates, 462 U.S. at 214 citing Draper v. United States, 358 U.S. 307 (1959). "Here, even standing alone, the facts obtained through the independent investigation of the Bloomingdale police officer and the DEA at least suggested that respondents were involved in drug trafficking. In addition, the judge could rely on the anonymous letter, which had been corroborated in major part by the police officer's efforts." Id. at 215.
To sum it up, the totality of the circumstances takes into consideration all the circumstances including "a balanced assessment of the relative weights of all the various indicia of reliability (and unreliability)" and commonsense. Id. at 234.