Reasonable Articulable SuspicionThis is where most of the standards have shaken out to. If you read back through old cases they are more protean because the language hadn't shook out yet, but you can usually see what they were developing into. So, in the modern era we've figured out the language and the appellate courts use the language and standards they have developed.
Clear & Convincing
Beyond a Reasonable Doubt
Of course they don't.
For most of us, this came to light last a couple years ago in Arizona v. Gant. In that case the US Supreme Court adopted a "reasonable to believe" standard when deciding the conditions that officers can search a car. If it is reasonable to believe that evidence of the crime the officer is arresting the driver for is in the car the officer can search the car. That is amorphous as all get out. Are they merely re-affirming the Carroll Doctrine? Or are they stating that reasonable articulable suspicion is enough under these particular conditions? The rest of us now get to fight over all of this for years because the Court couldn't bother to be clear.
However, it's not just the US Supreme Court which does this to us. Recently, I got a message from a fellow prosecutor who was arguing with a defense attorney over what the standard is in a probation violation hearing. I snapped off an answer, "Preponderance, because it is a post-conviction hearing." Of course, being lawyers, they weren't willing to take me at my word and the next thing I know, I'm looking through case law trying to support my position. As I look I realize that the answer I gave was based upon research that I had done about federal sentencing, not actual Virginia research.
Under Va. Code sec. 19.2-306, a judge can impose time which has previously suspended upon finding "good cause to believe that the defendant has violated the terms of suspension." So, the question becomes, what is "good cause?" Turning to the case law, I traced the standard to be applied to Slayton v. Commonwealth,185 Va. 357 (1946). In Slayton the Virginia Supreme Court stated that the standard is not beyond a reasonable doubt. Instead "revocation is a matter within the sound discretion of the trial court . . . reversible only upon a clear showing of abuse of such discretion." Abuse occurs when the judge does not use "conscientious judgment", instead taking "arbitrary action." A further gloss on this appears in Marshall v. Commonwealth, 202 Va. 217 (Va., 1960). In Marshall, The Virginia Supreme Court "[t]he cause deemed by the court to be sufficient for revoking a suspension must be a reasonable cause." So, splicing Slayton and Marshall together the standard for a probation violation is reasonable cause within the sound discretion of the trial court.
I don't know how anybody else reads that, but that language reads to me as tracking fairly consistently with the probable cause standard - "a level of reasonable belief, based on facts that can be articulated." That's an incredibly low standard. Perhaps this is because no one has actually challenged whether violations must be proven to a preponderance standard. It's a little disturbing to think that the standard is low enough that it could be less than 50% likely that the violation occurred.