Evidence of habit can be quite useful since it can help fill-in details forgotten by a witness in dealing with routine matters or procedures. This rule of evidence provides:

Rule 406. Habit; Routine Practice
Evidence of the habit of a person or of the routine practice of an organization, whether corroborated or not and regardless of the presence of eyewitnesses, is relevant to prove that the conduct of the person or organization on a particular occasion was in conformity with the habit or routine practice.

“Habit evidence is generally defined as [e]vidence of one’s regular response to a repeated specific situation.'” Carlson v. Warren, 878 N.E.2d 844, 850 (Ind. Ct. App. 2007) (quoting Black’s Law Dictionary 597 (8th ed. 2004)); See also 1 McCormick § 195 (2006). Evidence of habit can be very useful for handling standard procedures used by record keepers, medical personnel, police officers, lab technicians and toxicologists, where they cannot remember a specific item tested due to the volume of items processed. You simply have the witness outline their regular routine or practice in a particular situation to prove that they did so in your particular situation. (e.g. please describe your normal practice or procedure in performing the type of testing you performed here.)