Watch the Jumping To Conclusions online guitar lesson by TrueFire from Play Acoustic Guitar 7: Style Variations
Jumping To Conclusions - Performance is a video guitar lesson presented by David Hamburger and is sourced from Essentials: Fingerstyle Blues.
This kind of half-stepping into the chords happens all over the blues, at various tempos, and the compact three-note 13th chord voicings we're using here pack a lot of sound into just a few notes. If you've never encountered them before, it may take a little practice before you can just grab them quickly, but they don't use any more fingers than any open chord you know. That's what I tell myself, at least, when I run into some weird new voicing that's giving me fits.