Breath alcohol

• Author: James G. Wigmore
• Pages: 35-58

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 

Breath Alcohol

Breath alcohol analysis is commonly used in law enforcement as it has

many advantages over blood alcohol testing:

• Breath alcohol testing is noninvasive. No needles are required to

collect blood; hence, there is no possibility of injury or transmis-

sion of disea se.

• The breath alcohol results are known i mmediately, as opposed to

the several days or even weeks needed for blood results to be re-

ported by forensic laboratories. The police are therefore immedi-

ately aware of what charge to lay and whether medical treatment

may be required for the drink ing driver (e.g., alcohol poisoning).

• Breath alcohol correlates better w ith brain alcohol concentration

(arterial blood) and gives a better indication of impairment due to

alcohol duri ng the rising bloo d alcohol concentration (BAC) pha se.

• There are no continuity or storage and tran sportation issues. The

breath sample is provided directly into the breath alcohol instr u-

ment. No special blood tubes, swabs, identity seals, biohazard

refrigeration, or special transportation is required, as for blood

samples.

• No medical sta f‌f or phlebotomists are needed for breath alcohol

analysis. The breath tests may be conducted at the police station

or mobile van, allowing the time bet ween the arrest and testing

to be reduced signif‌icantly.

• There is no problem with a real or alleged blood or needle phobia

of the arrested driver.

36  The Abridged Wigmore on Alcohol

Reference Number: 

This chapter deals w ith the many issues that arise in cr iminal court,

such as the ability to provide a suitable breath sample, the blood-breath

ratio (BBR), the mouth alcohol ef‌fect, and the specif‌icity of breath alco-

hol tests.

3.01 METHODS OF ANALYSIS, DUPLICATION, AND

TRUNCATION OF RESULTS

Breath alcohol detection technology has changed dra matically over the

more than  years since the Breatha lyzer (using a wet chemical method)

was f‌irst introduced (, ). The chemical reaction that was t he

basis of the Breathalyzer wa s based on potassium dichromate (a yellow-

orange color) and sulfuric acid reacting with alcohol to form chromic

sulfate (a blue-green color), potassium sulfate, acetic acid, and water as

follows:

KCrO + HSO + CHCHOH →

Cr(SO) + KSO + CHCOOH +   HO

Electrochemical (fuel cell) sensors (–) also convert alcohol

into acetic acid but measure the electric current generated rather than

a colour change, as with the Breatha lyzer. Other devices use infrared

(IR; –) or a combination of the IR and fuel cells () to detect

breath alcohol. The n-type semiconductor (Taguchi) detector has been

found not to be suitable for evidential or even screening applications

(). Future methods of detection of alcohol may include portable

mass spectrometry (MS; ) or full IR spectrum scan (). The

dif‌ferences between two successive breath tests and the truncation of

breath test results are also d iscussed in this section (–).

Reference Number: 30101

, ..,  .. . “The Breathalyzer and Its Applications.”

Medicine Science and the Law, : –,  ( f‌igures,  references)

Reference Number: 30102

, .. “The Accuracy Reliability and Validity of the Breathalyzer.”

Australian New Zealand Journal of Criminology, : –,  ( tables,

 references)