CRONE, J.
Shepherd argues that his trial counsel’s assistance was impaired by his representation of Bobbie in an unrelated case. A criminal defendant’s Sixth Amendment right to effective assistance of counsel includes the right to conflict-free representation. . . . To prevail on a claim of conflict of interest, the defendant must demonstrate to the post-conviction court that trial counsel had an actual conflict of interest and that the conflict adversely affected counsel’s performance. Woods v. State, 701 N.E.2d 1208, 1223 (Ind. 1998) (citing Cuyler v. Sullivan, 446 U.S. 335, 348 (1980); Strickland, 466 U.S. at 692). Once a defendant has demonstrated an actual conflict and an adverse effect on his lawyer’s performance, the prejudice prong of an ineffective assistance claim is presumed. Id. (citing Burger v. Kemp, 483 U.S. 776, 783 (1987)).
An adverse effect on performance caused by counsel’s failure to act requires a showing of (1) a plausible strategy or tactic that was not followed but might have been pursued; and (2) an inconsistency between that strategy or tactic and counsel’s other loyalties, or that the alternate strategy or tactic was not undertaken due to the conflict.
Id.
Although the post-conviction court found that any conflict in trial counsel’s representation of both Shepherd and Bobbie was not significant, the State apparently concedes that there was an actual conflict of interest and argues only that Shepherd has failed to show that trial counsel’s performance was adversely affected. . . . .
Shepherd contends that there was an actual conflict of interest because (1) charges could have been brought against Bobbie for drugs and drug paraphernalia that were found in the house shortly after Shepherd’s arrest; and (2) the plea agreement reached in Bobbie’s pending case could have been rejected, and therefore, it “was clearly in her best interests to testify against Shepherd in a way that pleased the State.” . . . We conclude that Shepherd presents a prima facie case of actual conflict.
Shepherd then asserts that his trial counsel’s performance was adversely affected in that he failed to impeach Bobbie’s credibility by cross-examining her as to her pending charges and the amount of time she was facing without the as yet unfinalized agreement. It is true that Shepherd’s trial counsel did not ask Bobbie any questions at all regarding her pending case or any plea agreement she had with the State. We observe that “’[c]ross-examination is the principal means by which the believability of the witness and the truth of [her] testimony are tested.’” . . . We conclude that Shepherd has demonstrated that a plausible tactic or strategy was not followed due to the conflict.
. . . .
. . . Bobbie’s testimony was directly related to the ownership of the cigarette package containing cocaine that was in the car that both she and Shepherd had driven on the day in question. Her credibility was an important factor for the jury’s consideration. We therefore conclude that trial counsel’s assistance as to the possession of cocaine conviction was adversely affected by an actual conflict of interest. Because Shepherd has established an actual conflict and an adverse effect on his lawyer’s performance as to his possession of cocaine conviction, the prejudice prong of his ineffective assistance claim is presumed. See Woods, 701 N.E.2d at 1223. Therefore, as to Shepherd’s conviction for possession of cocaine, we reverse the post-conviction’s conclusion that Shepherd did not received ineffective assistance of trial counsel and remand with instructions to vacate that conviction. In all other respects the judgment of the post-conviction court is affirmed.
BAKER, C.J., and DARDEN, J., concur.