I know I should know this off the top of my head but....
We are investigating a murder. Defendant has already been arrested. We have been looking for the murder weapon across four counties for several days. We just learned a defense attorney is probably in possession of the weapon. I called and I am waiting for him to call back in an effort to get the weapon through his cooperation. What if he refuses or deny having it. I have enough PC for a search warrant but I am not realyy thrilled about rousting a defense attorney's office if I don't have to. What are his legal aand ethical obligations? I would think he had to turn over the weapon.

Looks to me like the attorney may be flirting with violations of Tex.Discip.Rules 4.01(b) or 1.05 (c)(4) or (d)(2)(ii), (f). Don't think he could rely on 37.09(b) either, since the weapon itself is not a privileged communication. See Sanford, 21 S.W.3d at 344 which cites a Michigan case for the following proposition: "attorney has a duty to turn over to the police physical evidence of a crime received during the representation of a client".

Rather than going to the trouble of a warrant, why not call the attorney and say,"we will obtain a warrant, but if the gun turns up in your possession, it sure looks like 37.09(a)(1) could cause you some trouble".

You might also look at Richard Anderson's paper from this summer's Advanced Crim. Law Course Chapter 33 at page 28-29. He lists several out of state cases where this has come up, including In re Ryder, 263 F. Supp. 360 (E.D. Va. 1967) (attorney suspended); Hitch v. Pima County Superior Court, 708 P.2d 72 (Ariz 1985);

see also Henderson v. State, 962 S.W.2d 544
(Tex. Crim. App. 1997) (maps); Clark v. State, 261 S.W.2d 339 (Tex. Crim. App. 1953) (instructions by defense counsel in how to get away with crime -- of destruction of evidence -- were not privileged).