MEMORANDUM***

Petitioner Larry Martin (“Martin”) brought some 118 habeas claims to the district court. With one exception, we find no apparent merit to those claims and affirm the denial of habeas relief. The lone exception is Martin’s ineffective assistance of counsel (“IAC”) claim, arising out of representations made to him by his trial defense counsel concerning the state’s plea offer and his sentencing exposure. Because we determine that Martin presents a colorable claim with respect to this issue, we remand it, and it alone, to the district court for an evidentiary hearing to determine whether Martin can demonstrate prejudice.

Martin’s claims were not defaulted in state court. Under Castillo v. McFadden, 399 F.3d 993, 998 (9th Cir. 2005), we look to petitioner’s briefing in the state court of last merits review to determine whether the claim has been “fairly pre*123sented” to the state courts. Among the claims set forth in his filings in the Arizona Court of Appeals, clearly present is Martin’s IAC claim regarding the representations of counsel concerning his sentencing exposure.

To understand Martin’s claim, it is necessary to unwind a factual mistake that began with the written plea offer and wound its way through the advice given Martin at the time of the offer, into the report of the magistrate judge and ultimately into the district court’s order rejecting the claim: Martin’s maximum exposure was forty-two years, not twenty-one years.1

Martin asserts that his counsel represented to him, based on the prosecutor’s plea bargain letter, that the maximum sentence for the robbery, should he go to trial, would be twenty-one years, when in fact it was forty-two years (as Martin was sentenced). Hill v. Lockhart, 474 U.S. 52, 57, 106 S.Ct. 366, 88 L.Ed.2d 203 (1985), applies the right to effective assistance of counsel under Strickland v. Washington, 466 U.S. 668, 104 S.Ct. 2052, 80 L.Ed.2d 674 (1984), to the plea process. Thus, Martin had the right to make an informed decision on whether to plead guilty or go to trial. See Nunes v. Mueller, 350 F.3d 1045, 1052 (9th Cir. 2003).

Under Hill, Martin’s burden is to show that his attorney’s performance was deficient in not properly informing him of his maximum sentence exposure. “[T]he gross mischaracterization” of the likely outcome of a case, “combined with the erroneous advice on the possible effects of going to trial, falls below the level of competence required of defense attorneys.” Iaea v. Sunn, 800 F.2d 861, 865 (9th Cir. 1986). For the prejudice prong, Martin “needed only to demonstrate that he had sufficient evidence for a reasonable fact finder to conclude with ‘reasonable probability1 that he would have accepted the plea offer, a probability ‘sufficient to undermine the result’ (Strickland, 466 U.S. at 694).” Nunes, 350 F.3d at 1054. While Martin presents a colorable claim, the problem in assessing both Strickland prongs is that neither the state court nor the district court provided Martin with an evidentiary hearing. Even respondent recognizes “the meager evidence on this issue.”

The district court recognized that if Martin was advised that his maximum sentence was twenty-one years for the robbery, “arguably that estimate was grossly disproportionate to the 42-year sentence that the trial court imposed.” Because of this, an evidentiary hearing is necessary to give Martin an opportunity to prove how his trial counsel erroneously advised him and to show a “reasonable probability” *124that he would have accepted the plea offer. Nunes, 350 F.3d at 1054.

AFFIRMED IN PART, REVERSED IN PART, AND REMANDED FOR AN EVIDENTIARY HEARING.