using keys from Dillon2 and Downie and Arnett, I believe this to be Hister depurator. Characteristics within the genus Hister leading to H. depurator include only 3 complete dorsal stria with #4 & 5 lacking almost entirely (not too common in Hister), subhumeral stria absent, 3-toothed protibia, and a few others. Both references list H. depurator's size as at most 6.0mm. However, Downie and Arnett include H. circinans Casey, who's short description and key seems to only differ from H. depurator in size of up to 7.8mm. I've since found several internet references to H. circinans being considered a synonym of H. depurator. Unless I'm missing something, I think H. depurator is correct.

taken from unbaited neglected pitfall trap half filled with mud