I agree that there is no way DW was going to turn himself in. I am baffled by the fact that he had been in contact with MPD. I wonder if that was actually him or someone pretending to be him.
ETA: sorry, bbm because I think you're brilliant!
As to why the defense is eager to make JW a crucial witness (I am not a criminal lawyer) - the charge DW is brought up on is felony murder, with the underlying felony being kidnapping. I believe the DC statute for kidnapping boils down to (a) holding someone against their will (b) in order to gain ransom or reward. You have to prove both parts.
Among other things, I think the defense is trying to say DW didn't commit a kidnapping (under the statute) because he never got a ransom or reward. No car, that was burned. Nothing found on him from the S house (per Detective Owens), so he didn't gain anything there. No cash, because (a) you cannot prove it was his (hence the trying to argue it was in closer to proximity to someone else - insert eye roll here) or in the alternative, (b) JW lied and never really dropped it off (and the money in the car came from "somewhere else"). I am not saying these are stellar arguments, just that these are the arguments the defense was throwing out there.
No ransom or reward, means no kidnapping occurred (under the statue), and if no kidnapping occurred, DW cannot be held on felony murder charge (District would have to try him for "plain old murder 1" which is a lot harder to prove than felony murder). I think the defense is trying to paint JW as a liar, and therefore why should you believe he actually dropped the money off in the first place. Or at least, that is part of the argument they will make.
And IIRC, it was said by Owens that there was no connection between JW and DW (I think he said this). If there is no nexus between the two, the part one plays in the felony cannot be attributed to the other under the statute (so if one did the holding and one got the reward, they can only be tied together under the felony murder statute if there was a "meeting of the minds" so to speak and if there is no connection between the two there could be no "meeting of the minds").
IMO, from what I learned in law school regarding felony murder.