I previously blogged about breath testing calibration in Chester County DUI's. An important case regarding this evidence is Commonwealth v. Mongiovi, 360 Pa. Super. 590.
The court ruled that that the nature of the charge against the defendant required the admission of technical evidence, that the jury had before it all the facts, including the breathalyzer results and the possible variance, and it was charged as to the necessity of finding defendant guilty "beyond a reasonable doubt." What this means is that the jury or judge needs the breath test and supporting documentation to conclude that the blood alcohol was beyond a particular level, establishing the standard of "beyond a reasonable doubt".
As the court stated, "The nature of the charge against appellant requires the admission of technical evidence. We see no other way for a jury to decide whether a defendant has reached a blood alcohol level of .10%."
The case continues to discuss how the jury should decide the "variance" which could imply a lower BAC. It is an issue that the jury must weigh in deciding their verdict when being defended by a Chester County DUI lawyer.
It also highlights that the breath testing equipment, pursuant to 67 Pa. Code § 77.25(a), where the equipment must be inspected within 30 days prior to using the breath test equipment.