As B.C. prepares to bring in tough new penalties for impaired driving, CTV News takes a closer look at some of the drawbacks of the Breathalyzer test.

Forensic scientist Nizar Shajani has one at home -- he often serves in court as an expert witness on the device.

"If it's properly operated, things will be fine, but we're not taking a blood sample, we're taking a breath sample," Shajani told CTV News.

When CTV reporter Jon Woodward rinsed with mouthwash and took the test immediately, he failed.

That's because the roadside screening device was measuring the alcohol in the mouthwash.

Last week, CTV reporter Mi-Jung Lee took a Breathalyzer test after drinking eight ounces of wine. The reading wasn't high enough for a criminal charge, but put her in the warning range between 0.08 and 0.05 blood alcohol content.

Beginning this fall, getting caught driving with an alcohol level that high could result in a three day driving ban.

For a complete rundown of the new drunk driving regulations, click here.

Lawyers call for more transparency

Anyone who's caught over the 0.08 limit may need to hire a lawyer like Paul Doroshenko.

He said that before tougher laws were enacted in 2008, defence lawyers had more leeway to question the accuracy of Breathalyzer tests.

"The problem is that every electro-mechanical device can potentially fail," Doroshenko said.

"The test could be inaccurate, so essentially, an innocent person could be convicted."

Defence lawyers have been battling to get the history and maintenance records of the instruments used to charge their clients.

A B.C. Supreme Court judge is now deciding whether that information has to be disclosed.

Meanwhile, Doroshenko says there are design flaws with a valve in the device that could give the wrong readings.

His Access to Information request garnered an internal email from Benny Wong, an RCMP forensic scientist with the force's toxicology services who is looking into the matter.

"How many innocent souls have been convicted with this instrument? Should I be quiet now?" Wong wrote in the email.

But when CTV News contacted the RCMP, they said they've conducted extensive testing, and have full confidence in the Breathalyzer.

"The instrument is basically what the lawmakers have said. [It gives] a true reading of what a person's blood alcohol level is," Sgt. Dave Savoy said.

Body temperature can affect readings

But Shajani, the forensic scientist, says that certain factors can impact Breathalyzer readings.

"This doesn't take into account body temperature. If somebody has a fever, for example, they can provide a higher reading," he said.

Given the tougher laws around impaired driving, Shajani added, "The best rule is, if you've had something to drink, don't drive."

Watch CTV News at Six for a report from CTV British Columbia's Mi-Jung Lee