Does the Constitution require a cumulative assessment of multiple constitutional errors at a criminal trial?

QUESTIONS PRESENTED FOR REVIEW Fermin Guerrero was convicted of the first-degree murder of Jose Ortiz and sentenced to fifty-years-to-life in prison, based on an informant’s testimony that Guerrero had supposedly confessed to the crime. But contrary to the informant’s testimony, eyewitnesses testified Guerrero was not the shooter and had a different face shape, body type, and complexion. Guerrero also had an alibi for the time period—earlier on the day of the crime—when the shooter was seen driving through the victim’s neighborhood. The prosecutor argued the eyewitnesses had recently fabricated their exculpatory testimony under pressure from Guerrero’s supposed gang associates, but a photographic lineup proved they had not done so. Guerrero’s trial counsel, however, inexplicably failed to present the photographic lineup to the jury to rehabilitate the eyewitnesses’ testimony that Guerrero was not the shooter. After trial, the state admitted that Guerrero’s prosecutor had failed to disclose to Guerrero’s defense that law enforcement had paid the informant between $6,000 and $10,000 for his assistance and testimony in Guerrero’s case. The jury never heard that information. The questions presented are: 1. Does the Constitution require a court on habeas review to assess cumulatively the prejudice caused by multiple constitutional errors at a criminal trial? 2. Did Fermin Guerrero suffer material prejudice from his prosecutor's undisputed failure to disclose to Guerrero’s defense that the prosecution’s key witness had been paid between $6,000 and $10,000 for assisting law enforcement in Guerrero’s case? 3. Did Guerrero’s trial counsel provide constitutionally ineffective assistance by failing to present evidence—contained in his own trial file—that would have rehabilitated the defense’s key exculpatory witness and rebutted the prosecution’s attack on her credibility? 4, Does the combined prejudice from the prosecution’s withholding of evidence and trial counsel’s ineffective assistance warrant relief from Guerrero’s conviction under the Fourteenth Amendment?