Psalm 37/Notes/Verbal.vv. 35-36.519703
"The perfective form may represent a past situation which the speaker is either unwilling or unable to specify precisely ("indefinite perfective")... Comrie refers to the 'experiential perfect,' which indicates 'that a given situation has held at least once during some time in the past leading up to the present'; Aspect, 58" (IBHS §30.5.1). Waltke and O'Connor suggest translating this particular verb (ראיתי) as a present perfect ("I have seen...", so NIV, NLT, ESV, CEV, NET, REB), but the following wayyiqtol verbs indicate that the psalmist is telling a story (with reference point movement) and that the qatal verb in v. 35a (ראיתי) is setting up the story, better translated as a simple past: "I once knew someone wicked... but later I passed by, and he wasn't there; I looked for him, but he could not be found" (GNT).