NCJ Number
198019
Journal
Canadian Society of Forensic Science Journal Volume: 35 Issue: 3 Dated: September 2002 Pages: 153-158
Date Published
September 2002
Length
6 pages
Annotation
This study examined the possible causes of the occurrence of the "INVALID SAMPLE" status message during breath sample delivery in the administration of the BAC (blood alcohol concentration) Datamaster Ctm.
Abstract
The manufacturer's 1997 BAC Datamaster Supervisor Guide explains the causes of the status code "INVALID SAMPLE" as due either to the subject's blowing saliva droplets into the sample chamber or to the presence of mouth alcohol. Based on this explanation by the manufacturer, some defense attorneys have suggested that if the possibility of saliva droplets can be excluded from the test, the only other cause of the "INVALID SAMPLE" must be mouth alcohol. Hence, any "INVALID SAMPLE" tickets generated during breath testing for blood alcohol concentration (BAC) would raise some doubt about the validity of the other test results. In order to obtain empirical data regarding the possible causes of the "INVALID SAMPLE" status code, an experiment was conducted during two Royal Canadian Mounted Police BAC Datamaster Ctm training courses. Police officers were given measured amounts of alcoholic beverages; they subsequently provided breath samples into a number of instruments. A total of 15 subjects were tested with different BAC Datamaster Ctm instruments. After being instructed to blow into the instrument with a specific exhalation pattern, 6 of the 15 subjects produced an "INVALID SAMPLE" status message. Considering the test protocol used and allowing for alcohol's disappearance from the mouth, the experiment demonstrated that the manner of sample delivery by the test subject (discontinuous manner of breath sample delivery) was the most likely cause of an "INVALID SAMPLE" status message during a BAC Datamaster Ctm breath test when mouth alcohol is not present. This finding magnifies the importance of the role of the qualified technician in carefully monitoring subjects while they are blowing into the instrument. 2 tables and 6 references