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Math in the Courtroom
Posted:
Aug 25, 2000 10:35 AM
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Recently, I served on a jury that heard a case involving a driver who had
been drinking and who had hit a black cow while driving on a dark, unlit
road at 1 AM. [I am not making any of this up] One of the things I noted
was how often mathematics came up and, unfortunately, how little about it
the attorneys for either side seemed to understand.
In our state, you can be convicted of DUI if your blood alcohol level is
0.08. The arresting officer apparently thought he had such a case because
he did not gather the kind of evidence at the scene that one would need to
prosecute a different kind of case. But by the time he got around to
testing the defendant, using the state's only approved breathalyzer
instrument, the blood alcohol level reported was just 0.07. Because the
prosecution called witnesses to support the accuracy and precision of the
instrument, as well as the state toxicologist, I at first thought they
were going to make some argument about how much the blood alcohol level
might have dropped in that two-hour period and still try to nail the
defendent on a DUI charge [in that case, other math would have come into
play because the several readings on the machine had to be within 10% of
their average, the temperature reading of something had to be 34 degrees
Celsius, and so forth]. But, it turned out that the prosecution had
changed its mind and wanted to try the defendent for "Negligent driving in
the first degree"--basically, driving in such a way as to endanger people
or property AND driving after drinking--no need to meet the 0.08 standard.
At this point, the type of math involved changed. One defense witness
[who had been riding in the pick-up truck involved] claimed he had first
noticed some cows in the road just after crossing an intersection. He
estimated that the distance to the cows had been about 150 feet. He
claimed that the driver had moved into the other lane and decelerated in
order to avoid hitting the cows he could see [they were black and white
cows], but that just after passing those cows they hit an all black cow
which they hadn't seen in the other lane. He also estimated that it took
about three seconds to cover the distance from the intersection to the
cows. Now, 150 feet in three seconds is OK--around 34 miles per hour [I
suspect the witness had had plenty of time to work all that out in the
preparation of his story]. But the prosecuting attorney kept referring to
the defendent covering 150 YARDS in three seconds--a high rate of speed
indeed for a small blacktop road on a dark night. At first, I assumed it
was just a slip of the tongue, but she kept doing it over and over. The
defense attorney objected to this and, of course the judge sustained.
But, then, the defense attorney tried to persuade the jury that his client
had been driving ONLY 66 Miles per second! [He could have made it coast to
coast during one commercial break]. Obviously he meant to say 66 feet per
second, which is 45 miles per hour--the posted speed limit on that road.
Again, it was probably a slip of the tongue, but I wonder. I suspect that
most of us--even had we made a slip of the tongue would have "heard" what
we said and realized that something did not sound quite right.
But what was bothering me--and which was never brought up by the
prosecuting attorney, is that the arresting officer had earlier testified
that the distance from the intersection to the "point of impact" where the
truck had hit the cow--was 0.15 miles. And we had a visual display hand
drawn by the officer showing the general lay out of the scene. Now I did
some mental math [the kind advocated by the NCTM Standards for elementary
students] and decided that it was "about 800 feet." So, I wondered if the
truck had actually gone 800 feet--not 150 feet during that estimated three
seconds. Or, even knocking 100 feet off to allow them to get past the
intersection, knocking another 100 feet off to allow for a difference
between first encountering the cows and having passed them, we're still
talking 200 feet per second--136 miles per hour! Had I been the
prosecuting attorney, I think I could have convinced the jury--using the
defense's own witness--that either the witness was very unreliable in his
recollections [because he had been drinking, also] or that the truck had
indeed been traveling at a very high rate of speed. But the prosecuting
attorney never said anything, and I believe it was because she never
realized what a large discrepancy there was between 150 feet and 0.15
miles.
To make a long story short, the most crucial information was never brought
up for discussion by the attorney, the visual with all the necessary
information was not available to the jury [I asked for it but it had never
been admitted as official evidence, so the request was denied], and so
because the jurors had "reasonable doubt" concerning the negligent driving
part, they found the defendent "not guilty." I personally suspect he was
guilty as hell.
Kind of makes you nervous concerning the future of our democracy, does it
not?
Ron Ward/Western Washington University/Bellingham, WA
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