The case is Diaz v. Kelly, actually several cases consolidated as they each raised the same issue. The government argued in this case that language deficiencies cannot toll the statute of limitations because many inmates have problems understanding English. Writing for the Court, Judge Newman disagreed:
We think the proper inquiry is not how unusual the circumstance alleged to warrant tolling is among the universe of prisoners, but rather how severe an obstacle it is for the prisoner endeavoring to comply with AEDPA’s limitations period. For the prisoner who cannot read English, the obstacle is undoubtedly serious, just as it would be for a prisoner speaking only English incarcerated in a non-Englishspeaking country, and can, in some circumstances, justify equitable tolling.
On the other hand, to take advantage of this equitable remedy, "the diligence requirement of equitable tolling imposes on the prisoner a substantial obligation to make all reasonable efforts to obtain assistance to mitigate his language deficiency." Two of the inmates before the Court of Appeals could not meet this test. While they cannot understand English sufficient to prepare their petitions and could not find anyone in the prison to help them, they did not show that they tried to get anyone outside the prison for assistance.
Better news for the other inmate whose case came before the Court of Appeals. As inmates first have to seek relief in the State courts before filing their Habeas petitions in Federal court, the problem is what to do when the State court does not inform the inmate that his case was decided and that it's time to bring the Federal case. The Second Circuit held that a prolonged delay by the State courts that the case was decided is enough to toll or extend the statute of limitations for the Federal Habeas Corpus petition. While the government argued that this inmate had a duty to inquire with the State court as to the status of his case there, the Second Circuit disagreed: "We see no point in obliging a pro se litigant to pester a state court with frequent inquiries as to whether a pending motion has been decided, at least until a substantial period of time has elapsed."