SAN DIEGO DUI DEFENSE: PARTITION RATIO DEFENSE LIVES! AT LEAST ON A CHARGE OF DRIVING UNDER THE INFLUENCE
A breath test measuring alcohol involves a conversion from breath to blood; that conversion is the partition ratio. The machine testing the breath is set with a standard, which is supposedly the human average: 2100 to 1.
But it turns out that partition ratios vary among people.
In Bransford (8 Cal.4th 885), the Cal. Supremes held that any evidence of variation was irrelevant to a charge of driving at or above .08, thereby barring the defense from presenting any evidence of variations in partition ratios.
But what about the (a) count? The Cal. Supremes hold, "If the defendant in a section 23152(a) case offers competent evidence showing that the use of a 2,100-to-1 conversion ratio may have yielded an inaccurate representation of his blood-alcohol level, introduction of this evidence is permissible."
So you CAN defend a DUI charge with a partition ratio defense; you just can't defend a .08 charge.
People v. McNeal; 2009 DJ DAR 10127; DJ, 7/10/09; Cal. Supremes
