Alcohol Testing in Forensic Context - Toxicology eCampusOntario VLS

Summary

This video script demonstrates the process of preparing standard ethanol solutions, calibrating an ethanol vapor sensor, and conducting analysis using the sensor. The script covers setup procedures for glassware, sensor calibration with two-point measurements, and real-time ethanol vapor analysis using graphical software. The script also includes case scenarios where ethanol levels are tested in unknown samples, simulating roadside breathalyzer tests in various situations. Each case explores different ethanol concentrations, ranging from low to high, and highlights the implications of the results for determining impairment. The video emphasizes accuracy, repeatability, and the need for additional testing in some cases.

Takeaways

• 😀 The preparation of standard ethanol solutions requires precise measurement and clean, sterile glassware to avoid contamination.
• 😀 The Go Direct ethanol vapor sensor is used to measure ethanol concentrations in the vapor above liquid ethanol samples, with an accuracy range of 0-3% ethanol.
• 😀 Proper calibration of the sensor is essential for accurate readings, using known ethanol solutions (0.05% and 1%) for a two-point calibration.
• 😀 The sensor is sensitive to vapor and requires a protective polyethylene tape to prevent damage from splashes. The tape should be replaced with each new sample.
• 😀 After calibrating the sensor, it is attached to a retort stand, and a black rubber stopper is used to secure the sensor above the ethanol sample for consistent readings.
• 😀 Calibration involves measuring the ethanol vapor in solutions, stabilizing the readings, and recording the results to ensure the sensor is accurate for future analyses.
• 😀 Data collection involves setting parameters in the software, such as sample duration (e.g., 300 seconds), and monitoring ethanol vapor levels in real-time during testing.
• 😀 The sensor allows for live tracking of ethanol vapor concentrations, which are graphically displayed in the software during analysis.
• 😀 In forensic cases, ethanol vapor levels are measured in duplicate samples to ensure reliability, and the results are saved for further analysis and documentation.
• 😀 Case studies, such as roadside DUI testing, demonstrate how ethanol vapor levels below or above the legal limit can indicate whether alcohol was a factor in impaired driving or if other substances may have been involved.

Q & A

What is the purpose of the Go Direct Ethanol Vapor Sensor?

The Go Direct Ethanol Vapor Sensor is designed to measure the concentration of ethanol in the air above an aqueous sample, providing accurate readings of ethanol levels between 0% and 3%, specifically in vapor form.

What should you do if splashing occurs during the use of the ethanol vapor sensor?

If splashing occurs, turn off the sensor and disconnect it. The polyethylene tape protecting the sensor should be replaced by the lab demonstrator. The tape can be changed by unscrewing the sensor tip, removing the old tape, and placing a new piece of tape carefully without twisting or folding it.

What is the significance of calibrating the ethanol vapor sensor?

Calibration of the ethanol vapor sensor ensures accurate and repeatable measurements. A two-point calibration using 0.05% and 1% ethanol solutions is performed to guarantee that the sensor can accurately measure ethanol levels within a relevant range, particularly for forensic analysis.

How should the sensor be set up for data collection?

To set up the sensor, connect the sensing wire to the sensor port and the USB end to a laptop. Then, position the sensor securely over a retort stand and place the ethanol sample bottle under the sensor with the neck of the sensor flat against the stopper to ensure consistency during readings.

What are the steps to perform a two-point calibration of the sensor?

To perform a two-point calibration, first calibrate the sensor using a 0.05% ethanol solution as the lower point. Wait for the stability reading to stabilize, then press 'keep'. Afterward, repeat the process with a 1% ethanol solution for the higher calibration point, ensuring accurate ethanol measurements.

Why is the ethanol vapor sensor calibration performed with small range values like 0.05% and 1% ethanol?

Small range values are used for calibration to ensure that the sensor is sensitive enough to measure forensically relevant ethanol concentrations, particularly in blood and urine samples where ethanol levels typically fall within this range.

How can the data collected from the sensor be saved?

Once the sensor has collected data for a specific ethanol concentration, it can be saved by naming the data file according to the corresponding concentration. The saved data can later be analyzed in detail.

What is the significance of measuring unknown samples in forensic cases?

Measuring unknown samples in forensic cases helps determine the ethanol concentration in biological samples, which is crucial for understanding the level of intoxication or impairment in individuals involved in legal cases such as traffic incidents or accidents.

How does the data collected from the ethanol sensor help in case scenarios?

The data collected from the ethanol sensor is used to simulate real-life case scenarios, such as traffic stops or accident investigations, to determine if the alcohol levels of a suspect are above the legal limit, potentially aiding in criminal investigations.

What should be done if the ethanol levels are close to the legal limit in a case scenario?

If ethanol levels are near the legal limit, further testing, such as urine or blood analysis, may be required to identify the presence of other drugs or factors contributing to impairment, as alcohol alone may not account for the behavior observed.