Witnesses before the grand jury, summoned to give evidence of any violation of this title, may be required to answer generally as to any such offense within their knowledge committed within 12 months next preceding, without being specially interrogated as to any particular offense, but no witness shall be prosecuted for any offense as to which he testifies before the grand jury, and any member of the grand jury or district attorney may be a witness to prove this fact.
Ala. Code § 37-8-4 (1975)