by Karl Denninger, Market Ticker:
As has been pointed out multiple times there is a presumption of innocence for all criminal investigations.
The prosecutor must find evidence of guilt sufficient to sustain a prosecution. This is well beyond probable cause; that just gets you a search warrant. To actually sustain a prosecution you actually need something beyond a preponderance of evidence — but exactly how far you must get beyond that point is a prosecutorial decision, mostly grounded in how much risk the department is willing to take of losing at trial.
Then the jury (or judge, if the accused so chooses) must find sufficient evidence to convict beyond a reasonable doubt.