Skip to content

Implementation of a Blind Quality Control Program in Blood Alcohol Analysis

Journal: Journal of Analytical Toxicology
Published: 2019
Primary Author: Jackeline Moral
Secondary Authors: Callan Hundel, Dayong Lee, Maddisen Neuman, Aimee Grimaldi, Maria Cuellar, Peter Stout

Declared proficiency tests are limited in their use for testing the performance of the entire system, because analysts are aware that they are being tested. A blind quality control (BQC) is intended to appear as a real case to the analyst to remove any intentional or subconscious bias. A BQC program allows a real-time assessment of the laboratory’s policies and procedures and monitors reliability of casework. In September 2015, the Houston Forensic Science Center (HFSC) began a BQC program in blood alcohol analysis. Between September 2015 and July 2018, HFSC submitted 317 blind cases: 89 negative samples and 228 positive samples at five target concentrations (0.08, 0.15, 0.16, 0.20 and 0.25 g/100 mL; theoretical targets). These blood samples were analyzed by a headspace gas chromatograph interfaced with dual-flame ionization detectors (HS-GC-FID). All negative samples produced `no ethanol detected’ results. The mean (range) of reported blood alcohol concentrations (BACs) for the aforementioned target concentrations was 0.075 (0.073–0.078), 0.144 (0.140–0.148), 0.157 (0.155–0.160), 0.195 (0.192–0.200) and 0.249 (0.242–0.258) g/100 mL, respectively. The average BAC percent differences from the target for the positive blind cases ranged from −0.4 to −6.3%, within our uncertainty of measurement (8.95–9.18%). The rate of alcohol evaporation/degradation was determined negligible. A multiple linear regression analysis was performed to compare the % difference in BAC among five target concentrations, eight analysts, three HS-GC-FID instruments and two pipettes. The variables other than target concentrations showed no significant difference (P > 0.2). While the 0.08 g/100 mL target showed a significantly larger % difference than higher target concentrations (0.15–0.25 g/100 mL), the % differences among the higher targets were not concentration-dependent. Despite difficulties like gaining buy-in from stakeholders and mimicking evidence samples, the implementation of a BQC program has improved processes, shown methods are reliable and added confidence to staff’s testimony in court.

Related Resources

Juror appraisals of forensic evidence: Effects of blind proficiency and cross-examination

Juror appraisals of forensic evidence: Effects of blind proficiency and cross-examination

Forensic testimony plays a crucial role in many criminal cases, with requests to crime laboratories steadily increasing. As part of efforts to improve the reliability of forensic evidence, scientific and…
Mock Jurors’ Evaluation of Firearm Examiner Testimony

Mock Jurors’ Evaluation of Firearm Examiner Testimony

Objectives: Firearms experts traditionally have testified that a weapon leaves “unique” toolmarks, so bullets or cartridge casings can be visually examined and conclusively matched to a particular firearm. Recently, due…
Mock Juror Perceptions of Forensics

Mock Juror Perceptions of Forensics

This CSAFE Center Wide webinar was presented on December 8, 2020 by: Brandon Garrett – L. Neil Williams Professor of Law, Faculty Director at the Wilson Center for Science and…
A Pioneer in Forensic Science Reform: The Work of Paul Giannelli

A Pioneer in Forensic Science Reform: The Work of Paul Giannelli

Few can say, “I told you so,” to our entire criminal justice system. Being right about what is wrong with the use of evidence in criminal cases is not a…