The Presentence Investigation Report cannot be amended after sentencing. That document is finalized and sealed as part of the court record, and there is no standard process for going back to add information that was withheld or omitted at the time of the original interview.
The advice your husband received from his attorney to withhold substance abuse history was poorly considered and has created a real problem. RDAP eligibility in the federal system requires documented evidence of a substance abuse disorder, and the PSI is one of the primary documents the BOP uses to make that determination. Without that documentation in the PSI, establishing eligibility becomes significantly harder, even if the history genuinely exists.
That said, the PSI is not the only path to RDAP eligibility. The BOP also considers medical records, prior treatment history, court documents that reference substance abuse, and in some cases, self-reporting evaluated by the facility's drug treatment staff. If your husband has medical records, prior treatment admissions, or any other documented history of substance abuse from before the PSI was completed, those records can be submitted to the BOP's drug treatment coordinator at his facility as supporting evidence for an RDAP application.
On the attorney's advice, an Ineffective Assistance of Counsel claim under the Sixth Amendment is the legal mechanism for challenging attorney conduct that materially harmed the defendant's case. Proving it requires showing both that the attorney's performance fell below an objective standard of reasonableness and that the outcome would have been different with competent advice. It is a difficult standard to meet but it is the appropriate vehicle if the withheld information genuinely cost him RDAP eligibility and the sentence reduction that comes with it.
A post-conviction attorney who handles federal sentence reduction matters is the right person to evaluate both the RDAP alternative documentation route and the ineffective assistance claim.