For New York DWI cases the government has the burden of going forward, the government has to prove their case beyond a reasonable doubt, and the government has to overcome the presumption of innocence.
Looking at the New York DWI Jury Instructions (the Judge instructs the jury with specific directions) for the per se charge (.08BAC or higher) VTL 1192 (2) states:
Under our law, evidence that the defendant operated a motor vehicle, and that thereafter the defendant had .08 of one per centum or more by weight of alcohol in his or her blood permits, but does not require, the inference that, at the time of operation of the motor vehicle, the defendant had .08 of one per centum or more by weight of alcohol in his or her blood.
In deciding whether to draw that inference (a likely conclusion drawn from the facts) you may consider the results of any test given to determine the alcohol content of the defendant's blood.
In this case, the device (it is a machine) used to measure blood alcohol content was a Datamaster DMT (usually). That device is generally accepted instrument (machine) for determining blood alcohol content. Thus, the People are not required to offer expert scientific testimony to establish the validity of the principles upon which the device (machine) is based.
NOW COMES THE GOOD PART:
In considering the results of any test given to determine the alcohol content of defendant's blood you MUST consider:
1. the qualifications and reliability of the person who gave the test;
2. the lapse of time between the operation of the motor vehicle and the giving of the test;
3. Whether the device (machine) was in good working order at the time the test was administered;
4. Whether the test was properly given.
Note: We can argue all the problems inherent with breath testing (an indirect measurement of blood alcohol), and all the problems with the machine.
Nevertheless, in evaluating the evidence offered to prove that the defendant did operate a motor vehicle while having a blood alcohol content of .08 or higher, you MAY consider, in addition to evidence of the results of the chemical test and the circumstances under it was administered, ANY evidence that, at times relevant to this charge, the defendant exhibited, or did not exhibit, signs of alcohol consumption.
Thus you MAY consider evidence of:
1. the defendant's physical condition and appearance,
2. balance and coordination,
3. manner of speech,
4. the presence or absence of an odor of alcohol,
5. the manner in which the defendant operated the motor vehicle (driving),
6. opinion testimony regarding defendant's sobriety,
7. the circumstances surrounding any accident.
The key of course with attacking the per se 1192 charge is going after the machine, it is not an instrument, not a device, it it "La Machina" and as such needs to be treated as such. It is not forensically reliable or accurate by any scientific standards or measure. Bringing this information (in simple terms) to the eyes and minds of the jury takes it off it's pedestal.
It is no more reliable than my vista software, my microwave, my vacuum cleaner, or my car on any given day. Accept those machines do not threaten me with jail, fines, probation, and alcohol treatment.