What is the test for disclosing an agreement with a District Attorney?

This case is governed by the principles applied by us in the remarkably similar case of United States ex rel. Washington v. Vincent, supra. There a witness denied having an agreement with the District Attorney when in fact the prosecutor had said he would "see what (he) could do to help him." We found that this was an agreement which should have been disclosed in response to the question put to the witness at trial of whether anyone had indicated that his testimony would get him favorable treatment from the District Attorney. We held that the prosecutor's failure to correct this false testimony violated the Fourteenth Amendment rights of the defendant and ordered the issuance of a writ of habeas corpus unless a retrial was granted.