When police suspect that a driver is under the influence of alcohol or drugs, they will pull them over and initiate a traffic stop. One of the things that the cop is almost guaranteed to do is ask the driver to take a breath test on a breathalyzer.

Not all of these breathalyzers are the same, though. The differences between the breath testing machines used on the road and those that stay in police departments are a big factor in how cases of driving under the influence (DUI) are investigated in Philadelphia.

Preliminary Versus Evidentiary Breath Testing Machines

During the traffic stop, a police officer who requests a breath test only has access to a preliminary breath testing machine. Also referred to as a portable breathalyzer, these are different in three ways from the evidentiary breath tests that are housed in police departments across Philadelphia:

1. Evidentiary machines are not portable
2. Evidentiary machines print out the results, while preliminary ones do not
3. Preliminary breath tests cannot be used as evidence

Portability

The most obvious difference between the two is that preliminary breath testing machines are portable, while evidentiary ones are not. Preliminary tests are done on what people tend to think of when they hear the word “breathalyzer” – a hand-held machine weighing less than a pound, with a funnel-shaped mouthpiece.

Evidentiary testing machines, on the other hand, are around the size of the average computer printer. They are unwieldy, heavy, and, most importantly, they need to be plugged into an electrical outlet to work. Because they can't feasibly be taken out on the road, police have to rely on preliminary testing machines, first.

Paper Trail

Breath samples that get analyzed in evidentiary machines in the police department lead to a printed report that includes the breath alcohol content in the sample. Breath tests that are done with a preliminary machine, on the other hand, only lead to a reading on a tiny display screen.

Admissibility as Evidence

Because they produce no paper trail, the results of a preliminary breath testing machine cannot be admitted as evidence in a DUI case. This avoids the tricky situation where a police officer has to remember the reading on the display screen, raising important questions about his or her memory and their credibility.

Instead, the function of a preliminary machine is more to give the officer at the traffic stop an indication that the driver might be under the influence and in need of further investigation. Readings above the legal limit, or even close to it, can be used to justify a decision to make an arrest at the traffic stop and bring the driver into the station for a test on the evidentiary testing machine.

LLF Law Firm: DUI Defense in Philadelphia

LLF Law Firm are criminal defense lawyers who represents the accused in Philadelphia, including people accused of drunk driving. Contact them online or call the law office at 888-535-3686 for help defending against an allegation that you were driving while under the influence.