Criminal Procedure Act, 1977 (Act No. 51 of 1977)
Chapter 23 : Witnesses
194. Incompetency due to state of mind
No person appearing or proved to be afflicted with mental illness or to be labouring under any imbecility of mind due to intoxication or drugs or the like, and who is thereby deprived of the proper use of his reason, shall be competent to give evidence while so afflicted or disabled.