Know Your DUI Expert

Let me tell you a tale of two contrasting DUI cases. Both where the attorney and I have worked together in the past. One where the attorney prepped with me in advance, and the second when the attorney didn't

In the first case, based on incredibly good performance on a dash-board patrol camera, the defense attorney was able to asked me questions that lead the jury to have enough reasonable doubt for a full acquittal. That's impressive enough on most DUI cases, in this case the defendant was charged with:

1) Impaired to the slighted degree

2) BAC over 0.08 within 2 hours of driving

3) BAC over 0.150 within 2 hours of driving (AZ Extreme DUI)

4) BAC over 0.200 within 2 hours of driving (AZ Super Extreme DUI)

The attorney in this case is arguably one of the best litigating DUI attorneys in the southern Arizona area. The evidence against the subject was a blood reading of 0.265.

In the second case I wasn't prepped properly for trial. I had read the case material, and in my case notes I had written that the case seemed very weak, and the subject's (who's blood reading was a 0.146) best possible outcome was very likely a regular DUI charge.

There was a lot of documented behavior in the case that would lead to very poor jury appeal.

The issue in the case was that the blood draw occured over 3 1/2 hours after driving. The attorney got me on the stand and made sure I was aware (and the jury was aware I was aware) of the time line of the case. The theory of the case for the defense was that a retrograde extrapolation (a back calculation/prediction of the subjects BAC earlier in time) can't be done from 3 1/2 hours after the time of driving.

His question was something of the effect of - Isn't it true that there is no way to give a reasonable scientifically accurate retrograde extrapolation 3 1/2 hours after driving, and with no eating or drinking history?

My answer was something to the effect of - "Accurate scientific and retrograde extrapolation" are oxymorons. Be that as it may, without an eating and drinking history, in Arizona it is still generally accepted to retrograde back to the time of the stop +2 hours. Some police scientists might go an hour, others might even go a half hour, but 2 hours would be fine, but we have to remember that based on the literature, the individual's calculated BAC could over-estimate their actual BAC by as much as 10% if they aren't fully absorbed at stop +2 hours.

This wasn't the answer the attorney was expecting, and it basically tanked his case.

Always remember to talk to your expert before they get on the stand. The state's expert can hurt your case, but your own expert can destroy it even quicker if you don't know what their opinions are, and you make assumptions.