In general

• Every person is competent to be a witness except as otherwise provided in these rules or by statute.

Evid. R. 601

• The general rule is that a witness is clothed with a presumption of competency.

Gosnell v. State, 376 N.E.2d 471, 472 (Ind. 1978)

• It is a general principal of law that everyone is presumed to be competent.

Walker v. State, 986 N.E.2d 328, 333 (Ind. Ct. App. 2013)

• A witness’s intoxication at the time of the events about which he is to testify goes to his credibility, rather than to his competency.

See Jones v. State, 445 N.E.2d 92, 93 (Ind. 1983)

• A witness is competent if he has sufficient mental capacity to perceive, to remember and to narrate the incident he has observed and to understand and appreciate the nature and obligation of an oath.

Boyko v. State, 566 N.E.2d 1060, 1062 (Ind. Ct. App. 1991)(citing Ware v. State, 376 N.E.2d 1150, 1151 (1978))

• [D]rug use per se does not render a witness incompetent to testify.

Boyko v. State, 566 N.E.2d 1060, 1062-1063 (Ind. Ct. App. 1991) [Here, the court cites to a number of other jurisdictions for this proposition, and implicitly adopts this rule.]

See also Crocker v. State, 563 N.E.2d 617, 623 (Ind. Ct. App. 1990)(“A witness's drug abuse would be pertinent only as to the witness's ability to recall events on the dates in question had he been using drugs at that time, or if the witness was on drugs at trial, or if drug abuse was so extensive as to impair the witness's mind.”)

• Questions about the character or sobriety of a witness, of course, go to the weight of that witness' testimony and not to its admissibility.

Bieghler v. State, 481 N.E.2d 78, 85 (Ind. 1985)