DUI cases make up the bread and butter of most criminal dockets. One of the primary evidentiary tools for these cases is some sort of BAC testing instrument. Like any piece of scientific equipment though there is a margin of error inherent in the testing procedure and equipment. This margin of error has been the source of significant litigation across the United States, where defense attorneys have attempted to introduce the testing margin of error as something for the jury to consider when analyzing the BAC test. There is a majority and minority view held by the sister-states concerning the admissibility of blood alcohol test margin of error. The majority view is that margin of error is admissible and can be considered for the weight of the evidence, the credibility of the evidence, or for attacking a statutory presumption of intoxication. The minority view is that the margin of error is inadmissible because the statute already takes it into account or only goes to the validity of the test and not to its evidentiary value. It should be noted though that the following is not a complete survey of all fifty states, because some states do not have as extensive case law on point or dip into administrative or civil license forfeiture decisions for basing their analysis on BAC testing margin of error.
A. The Majority Margin of Error View
There are at least eighteen states that find that evidence of margin of error in blood or breath alcohol testing is admissible at trial. Some states have found that the margin of error of a testing device can provide reasonable doubt. Others find that any evidence of a possible margin of error in the testing equipment or procedure is admissible for determining either the weight of the test evidence provided by the prosecution, the credibility of the test evidence, or rebutting statutory presumptions of intoxication. The eighteen states that use the majority view on margin of error are Arizona, California, Florida, Georgia, Hawaii, Kansas, Kentucky, Maine, Michigan, Montana, Nebraska, New York, Ohio, Pennsylvania, Texas, Utah, Vermont, and Washington.
Margin of error evidence has been accepted to be a factor towards the weight of testing evidence. The defendant in Hammontree argued that his blood alcohol test results were inadmissible because of the margin of error inherent in the device, but the court was unpersuaded.
Some states that allow blood alcohol test margin of error evidence find it admissible to attack statutory presumptions of intoxication. The Arizona Court of Appeals found that because the jury must find beyond a reasonable doubt that the defendant’s blood alcohol level exceeded the statutory amount, evidence of any margin of error was one more piece of evidence for attacking the statutory presumption of impairment.
As justification for permitting margin of error evidence, some courts have emphasized the importance of proving all elements of an offense beyond a reasonable doubt as a strong justification. The Hawaii Court of Appeals determined that margin of error evidence was admissible because it read the statute defining presumptions of intoxication strictly, reiterating that it was the prosecution’s burden to prove beyond a reasonable doubt that the defendant’s actual blood alcohol content was above the statutory limit rather than simply what the test results showed. The court explained that the introduction of margin of error evidence was not just admissible but an important factor that the prosecution must refute in order to ensure a conviction. In Prestier, the court held that since chemical tests are used for prosecution of driving under the influence that for the sake of the fairness any margin of error in testing must be strictly construed against the state and liberally construed in favor of the defendant.
B. The Minority Margin of Error View
In the minority of sister-states, courts have chosen to disregard the margins of error of blood alcohol tests because the statute either integrates the margin of error in it already as seen through clear legislative intent or that the margin of error only goes toward the test’s validity not to its evidentiary value. There are five states that follow this minority view; Alaska, Delaware, Massachusetts, New Jersey, and North Carolina.
Alaska has the strongest rationale for their refusal to admit margin of error evidence, and that is because the legislature specifically revised the statute in response to the Alaska Supreme Court decision in Haynes v. State, which allowed margin of error evidence to be admissible.
Delaware also disregards evidence of margin of error because the statute specifically bars margin of error evidence from being introduced to challenge the test. The court found this to be a clear showing of legislative intent to bar margin of error evidence. The Appeals Court of Massachusetts found margin of error evidence to be inadmissible because the margin of error stated by the Department of Public Health is merely the minimum and not necessarily the actual margin of error of any given testing device, and that the margin of error goes to the validity of the test not its evidentiary value.
Finally, the New Jersey Superior Court Appellate Division’s rationale for the inadmissibility of margin of error evidence in per se offenses is rooted in the legislative purpose of the statute. In addition, the court chose to ignore sister-state jurisprudence on margin of error because it felt this case was so clearly guided by state legislative purpose. The court also sought to avoid a battle of the experts for every DWI case.
The motive of this piece is to provide some sense of where the sister-states fall on the issue of BAC margin of error. This information can provide the basis for further research for various types of motions or objections. Ultimately, it is vital that every attorney check how her particular state treats BAC testing margin of error if she wishes to attempt to use it in court. Most commonly it is treated like any other piece of evidence, admissible with a proper foundation, and there to attack the credibility of the BAC test itself. However, admissibility is not the universal rule, and should never be assumed as such.
Senior Staffer, Criminal Law Practitioner
Image by Oregon Department of Transportation (breath test uploaded by Smallman12q), via Wikimedia Commons.
 See Com. v. Lippert, 887 A.2d 1277, 1281 (Pa. Super. Ct. 2005) (given the margin of error of the testing device the possibility that the defendant’s blood alcohol content was the exact statutory limit created too weak of a ground to establish guilt beyond a reasonable doubt).
 See Hammontree v. State, 512 S.E.2d 57, 58 (Ga. App. 1999) (“The fact that a testing procedure has some margin of error or may give an erroneous result under certain circumstances relates to the weight, rather than the admissibility, of the test results.”); See also Com. v. Davis, 25 S.W.3d 106, 108 (Ky. 2000) (“The Intoxilyzer test results should be admitted into evidence, and any problems with the simulator component of the device should go to the weight of such evidence, rather than its admissibility, when the calibration unit and testing unit are in proper working order on the testing date.”); State v. Gai, 288 P.3d 164, 169 (Mont. 2012) (the Intoxilyzer's margin of error went to “the weight of the test evidence, not the admissibility of the test results”); Morris v State, 214 S.W.3d 159 (Tex. 2007)(an expert’s testimony about a testing device’s margin of error is admissible if it is admissible under Daubert analysis); State v. McMahon, 557 A.2d 1324, 1326 (Me. 1989) (the court did not dispute the defense evidence that the Intoxilyzer test had a margin of error of approximately plus or minus .02% and was admissible).
 See State ex rel. McDougall v. Superior Court In & For County of Maricopa,875 P.2d 203, 205 (Az. Ct. App. 1994) (emphasizing that actual blood alcohol content was a question for the fact finder and all evidence must be considered); See also People v. Randolph, 213 Cal. App. 3d Supp. 1, 11, 262 Cal. Rptr. 378, 384 (Ca. App. Dep't Super Ct. 1989) (holding that margin of error evidence from an expert witness was admissible as another factor for the jury to consider in determining beyond a reasonable doubt); State v. Cooper, 391 So. 2d 332, 333 (Fla. Dist. Ct. App. 1980) (stating that margin of error would have been an important factor if the samples had not been destroyed ); People v. Jagotka, 622 N.W.2d 57 (Mich. 1999) (the defendant had the ability, even after the blood sample was destroyed, to impeach the test result by raising questions about “equipment condition, margins of error, compliance with testing norms and practices, and human error”); People v. Cancel, 520 N.Y.S.2d 509, 513 (Crim. Ct. 1987) (the jury was confronted with the issue of whether to give weight to the breathalyzer reading, given the possibility that the margin of error came into play); City of Orem v. Crandall, 760 P.2d 920, 924 (Utah Ct. App. 1988) (margin of error can be used for rebutting the statutory presumption of intoxication) (overruled on other grounds)); State v. Lowe, 740 A.2d 348, 351 (Vt. 1999) (margin of error was admissible for rebutting the statutory presumption of being above the legal limit).
 See State v. Boehmer, 613 P.2d 916, 918 (Haw. App. 1980) (citing State v. Bjornsen, 271 N.W.2d 839, 840 (Neb. 1978) (“[I]t is a judicial determination as to whether this evidence is sufficient to sustain a conviction, if the evidence is believed. The Legislature has selected a particular percent of alcohol to be a criminal offense if present in a person operating a motor vehicle. It is not unreasonable to require that the test, designed to show that percent, do so outside of any error or tolerance inherent in the testing process.”).
 See State v. Prestier, 455 N.E.2d 24, 27 (Ohio Mun. 1982); See also State v. Finch, 244 P.3d 673, 679 (Kan. 2011) (“A defendant may raise and argue margin of error or other questions about the reliability or accuracy of his or her blood- or breath-alcohol concentration [.] Margin of error is simply a factor among many possibilities for the fact-finder to consider.”).
 See Bushnell v. State, 5 P.3d 889, 891 (Alaska Ct. App. 2000) (following Haynes, the legislature enacted AS 28.40.060 which states that if within four hours of driving, the driver is tested on a properly calibrated, properly functioning Intoximeter and the driver's test result is at least .10 percent blood-alcohol or the equivalent .10 grams of alcohol per 210 liters of breath. “The fact that the driver's true blood-alcohol or breath-alcohol level may be slightly lower due to the Intoximeter's acknowledged margin of error it is no longer relevant to the driver's guilt under AS 28.35.030(a)(2)”).
 See Rebarchak v. State, 825 A.2d 239, 239 (Del. 2003)(citing 21 Del. C. § 4177(g) “In any proceeding, the resulting alcohol or drug concentration when a test, as defined in subsection (c)(2) of this section, is performed shall be deemed to be the actual alcohol or drug concentration in the person’s blood breath or urine without regard to any margin of error or tolerance factor inherent in such tests.”).
 See Com. v. Rumery, 940 N.E.2d 1251, 1255 (Mass. App. Ct. 2011)(the actual margin of error of the testing device in the case was .0004 and an instruction about the .01 margin of error minimum would have misled the jury).
 See State v. Lentini, 573 A.2d 464, 466 (N.J. Super. Ct. App. Div. 1990)(citing State v. Tischio, 527 A.2d 388 (N.J. 1987)(“The overall scheme of these laws reflects the dominant legislative purpose to eliminate intoxicated drivers from the roadways of this State. [T]he determination of blood-alcohol levels through chemical or breathalyzer tests is the linchpin of New Jersey's drunk-driving statutes. N.J.S.A. 39:4-50(a).... expresses a clear legislative purpose to rely exclusively upon breathalyzer test results whenever possible.”).
 Id. at 467 n.4.
 Id. at 467 (when referring to the bright line rule for per se offenses and presumptions of intoxication in the statute “[T]he primary purpose behind the 1983 Amendment to the statute was to streamline the administration of the penal and regulatory laws in this area by eliminating the necessity for expert testimony at trial.”).