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Citation |
Langille RM, Patrick J. J. Can. Soc. Forensic Sci. 2006; 39(2): 55-64. |
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Copyright |
(Copyright © 2006, Canadian Society of Forensic Science, Publisher Informa - Taylor and Francis Group) |
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DOI |
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PMID |
unavailable |
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Abstract |
In a retrospective study, Intoxilyzer® 5000C results obtained over a four year period by qualified breath technicians of the Toronto Police Services (TPS) between 1995 and 1998 were analysed and compared for the precision between untruncated and truncated duplicate breath tests. A total of 8585 breath tests were analysed. Of these, 8309 (97%) were found to be within 20 mg/dL untruncated, versus 276 (3%), that were within 21 to 29 mg/dL. The mean absolute (unsigned) difference between subject tests that were within 20 mg/dL untruncated for all four years was 7.05 ± 4.91 mg/dL (mean ± sd). After truncation, only 178 or 2.07% of the tests that differed by an absolute value of 21-29 mg/dl were rendered 20 mg/dL apart. Most of the rejected values were from the range of 25-29 mg/dL different, skewing the acceptable data significantly towards the 21-22 mg/dL range. Truncation thus does not randomly render acceptable differences between breath tests of 21 to 29 mg/dL and this procedure retains scientific relevance and does not unfairly prejudice drinking drivers. These results reveal that properly trained qualified breath technicians operate the Intoxilyzer® 5000C with a high degree of precision, resulting in 97% of all paired subject tests being within 20 mg/dL of each other using the untruncated values. |