OPINION
Yong Wei Liu is a native and citizen of the People’s Republic of China. He entered the United States from Mexico in August 2002. In December 2002, the Government charged him as removable as an alien not admitted or paroled into the United States. Liu conceded removability but sought asylum, withholding of removal, and protection under the Convention Against Torture (“CAT”).
In his application and in his testimony before the Immigration Judge (“IJ”), Liu claimed persecution on the basis of his participation in an underground church in China and his evasion of arrest for church activities. The IJ denied Liu’s application. Although the IJ believed Liu’s explanation of how and when he arrived in the United States, the IJ otherwise made an adverse credibility finding based on a birth certificate issued when Liu was in hiding in China, a minor inconsistency about the date of the underground church incident (although the IJ acknowledged that the inconsistency could be a translation error), and the implausibility of Liu’s escape from police. Allowing that “a reviewer of [the] record could conceivably conclude, unlike [the IJ], that [the credibility concerns] are not sufficiently substantial to justify an adverse credibility finding,” R. 36, the IJ went on to state that the credibility concerns at least raised the question of whether Liu had adequately corroborated his claim.
The IJ was not troubled by the absence of corroboration as to when Liu arrived in *626the United States, finding his testimony credible on that point. However, the IJ concluded that Liu’s wife should have testified to corroborate his claim because she knew what happened to him in China and visited him while he was in hiding there. The IJ did not accept Liu’s explanation that it would be too emotionally trying for her to testify because she was five months pregnant. The IJ concluded that even if all credibility doubts were resolved in Liu’s favor, Liu had not met his burden to show past persecution because he failed to corroborate the “core of his claim” (and “not just [his] religious affiliation”). R. 39. The IJ acknowledged that Liu had produced letters from his parents, his cousin, and his pastor, and noted that in many cases it would be unreasonable to expect additional corroboration, but believed it was reasonable to expect Liu’s wife to testify. The IJ concluded that without her testimony, Liu had not met his burden to qualify for asylum. The IJ likewise concluded that Liu did not meet the higher standard for withholding. The IJ separately rejected the CAT claim, concluding that there was insufficient evidence that Liu would face torture on his return to China because of how he left the country. Liu appealed to the Board of Immigration Appeals (“BIA”). In a short order, the BIA adopted and affirmed the IJ’s decision.
Liu petitions for review. He argues that the IJ and the BIA erred in finding that he failed to demonstrate a well-founded fear of persecution based on his religious beliefs and the altercation with the police officers. He contends, as well, that the IJ substituted his personal beliefs for evidence and claims not only that there was no basis for an adverse credibility finding, but that the absence of his wife should not have been used as a basis for a negative credibility finding. He asks that this matter be remanded for further proceedings on his asylum, withholding, and CAT claims.1
Because the BIA relied on the IJ’s reasoning, the decisions of the BIA and the IJ *627both must be considered. See Chen v. Ashcroft, 376 F.3d 215, 222 (3d Cir.2004). We review questions of law de novo, see Gerbier v. Holmes, 280 F.3d 297, 302 n. 2 (3d Cir.2002), and we review factual findings for substantial evidence, see Butt v. Gonzales, 429 F.3d 430, 433 (3d Cir.2005).
The IJ first rejected Liu’s claim as to the adverse credibility determination. Like other factual findings, an adverse credibility determination must be afforded substantial deference, so long as it is supported by sufficient, cogent reasons. See Butt, 429 F.3d at 434. We must evaluate whether the credibility determination was “appropriately based on inconsistent statements, contradictory evidences, and inherently improbable testimony ... in view of the background evidence on country conditions.” Chen, 376 F.3d at 223.
In part, the credibility determination is built on uncertain fundament. Liu’s recitation of the police attack for underground church activities remained the same throughout the immigration proceedings. There is the minor factual inconsistency identified by the IJ in the record— the May 6, 2002 date cited by Liu’s cousin in a letter (which, as the IJ noted, could be a translation error).2 Such a minor inconsistency alone would not merit the adverse credibility determination. And the other basis for the IJ’s conclusion — the implausibility of Liu’s escape — does not provide much support because it may have been based on an error and otherwise borders on speculation. The IJ mischaracterized Liu’s testimony when he reported that Liu stated that he escaped by the front door, R. 24; Liu maintained that he left by the back door. The IJ also wondered how Liu managed to escape arrest after hitting a police officer in a scuffle, but Liu’s testimony about his escape was not inherently improbable. According to Liu, his father interfered with efforts to capture him, and the police were outnumbered by the church members, all of whom were involved in the argument. As the IJ noted, Liu also got away from the officers despite falling twice, but, from his testimony, he appeared to have at least a small lead on the officers on leaving his house, and he was a young man familiar with the landscape.
The third basis for the credibility finding raises some doubts about Liu’s account. The date of issuance of the birth certificate is curious. Liu could not explain why it had been issued when he was in hiding. R. 150-53. Why would Liu risk obtaining a notarized birth certificate from the Chinese government while he was in hiding? Was Liu trying to hide from the IJ his own efforts to get his birth certificate in advance of his departure from China? Or was Liu dissembling when he stated that someone else obtained it and a young boy brought it to the country because Liu wanted to hide the fact that he had submitted a fraudulent document, as the IJ suggested? The notarization date on the birth certificate appears to be contradictory evidence in support of the IJ’s finding. However, the date of issuance does not go to the heart of Liu’s claim, which is his claim of past persecution based on underground church activities.3 (It may none*628theless undermine a claim of future persecution, as it suggests the possibility that Liu was not in hiding.)
Considered together, the current bases for the credibility finding fall short of being sufficient, cogent reasons. The IJ suspected as much, R. 86, so he tried to fortify his decision by concluding that even if Liu had been a credible witness, he had not properly corroborated his claim. However, the IJ’s request for corroboration was not reasonable under the circumstances.
“In general, it is reasonable to expect an applicant to corroborate facts which are central to his or her claim and easily subject to verification.” Kayembe v. Ashcroft, 334 F.3d 231, 238 (3d Cir.2003) (citations omitted). Liu provided corroboration of the facts central to his claim (the letter from his parents, for example). The IJ, however, wanted Liu’s wife to testify. The IJ explicitly decided not to “comment on what the wife might have testified to,” but based his alternative conclusion that Liu could not meet his burden to show eligibility for asylum based on the “evidentiary gap” caused by the absence of Liu’s wife’s testimony. R. 40. However, although his wife was admittedly close to the hearing site and could have appeared (albeit pregnant), she was not privy to facts central to Liu’s claim of past persecution. Although she knew Liu had been in hiding, she was not present when the police arrived at the underground church service. Perhaps she could provide information about the possibility of future persecution, but she could not provide details about any past persecution, which seemed to be the focus of the IJ’s analysis. Without those details, it is difficult to see how she could have been “a star witness,” as the IJ concluded. R. 39.
We do not comment on whether Liu should ultimately succeed on his claim for asylum. However, because of the infirmities in the credibility and corroboration analysis, we will grant the petition for review. We will vacate the BIA’s order and remand this matter to the BIA for further proceedings consistent with this opinion.