If the place he applied to sent you his resume, it sounds to me like they probably want you to verify what he said he did at your work. If he lied about what he did while working with you, you should give the company he applied to the correct information. If he doesn’t get the job because he lied, its pretty much his own fault. Companies ask for references and employment history for a reason—so they can verify that you did indeed work for this company and that you did indeed perform all the tasks described on your resume.
If he was truthful about what he said he did with you, but lied elsewhere on his resume, I don’t think you should say anything. Like @gemiwing said, its up to the employer to find out the truth about his other skills and work/education history.