[glaugh]

Here's Robert Hare, the expert on this stuff:

"We refer to individuals with a very high concentration of these features (perhaps 1% of the general population) as psychopaths" [1]

So there's no clear cutoff, it's not a bimodal distribution, but if you are in the top 1% (of a professionally administered version of this test) you might be considered a psychopath.

[1] http://www.psychopathysociety.org/images/hare%20commentary%2...