Want to get out of jury duty? Become a chemist.

A few months ago I received a jury duty summons from Los Angeles County. I was unhappy that I’d be out of the lab for several days if selected, but excited to have my first personal look into our legal system.

For those of you who have not yet been summoned, I’ll share with you a general description of my experience. The first step is to wait. I sat in a room with a few hundred other people for five hours before I, along with 60 other people, were called to a courtroom to begin the selection process.

Inside the courtroom sat the potential jurors, the prosecution/defense, the suspect, judge, bailiff and court reporter. They observed while I and the other potential jurors swore to answer all questions truthfully. Twenty of us, (everyone is assigned and referred to by a number. I was ten) were called to the jury box. The case involved a driving under the influence (DUI) charge and one by one the jurors were required to answer a series of general questions (Do you know anyone in law enforcement? What is your occupation? Do you have any strong feelings about the charges? Etc.). When asked my occupation I responded that I was a graduate student in chemistry.

After the general questions both the prosecution and defense asked additional questions, some directed to particular individuals. The questions attempted to uncover the jurors preconceived notions about the suspect and crime. One question asked by the defense sparked my attention. The attorney asked, “Does anyone know how breathalyzer works?”

Although a simple concept that can be grasped by any general chemistry student, the most common portable breathalyzer is actually a very clever use of electrochemistry. Inside of the device is an electrochemical cell operating at a constant potential:

At the cathode, oxygen is reduced in the presents of water to produce hydroxide ions.

O2 + 2H2O + 4e –> 4OH

At the anode, the ethanol in your breath is oxidized to acetic acid.

CH3CH2OH + 4OH –> H3CCOOH + 3H2O + 4e

Because this is a well defined 4 electron process, the current produced can be used to determine the amount of ethanol in your breath.

In response to the defense attorney’s question, I raised my hand, prepared to explain the chemistry behind the device. Unexpectedly, the lawyer turned to me and, as if already aware of my answer, dismissively said, “I will get back to you later.”

After 10 minutes the defense lawyer returned to me and delivered the following two questions:

1)  “It is the responsibility of a juror to leave any expertise at the door and make their decisions based only on what is presented by witnesses called during the trial.  This also includes not discussing your external knowledge with fellow jurors. Can you, even if you know the testimony of one of the experts is wrong, make your decision based only on what is presented?”

My answer: Yes. (Internal monologue: I can but I would lose sleep at night knowing I allowed a potentially innocent person to be punished.)

2)  “While hearing a testimony that contains information you know to be false you might instinctively think “that is wrong and this is why.”  Can you stop yourself from having these thoughts?”

My answer: No. (Internal monologue: Is that even possible?)

Following a meeting between the judge, prosecution and defense, the first three jurors were dismissed. I was one of them, along with a man who could not speak English and a woman whose best friend had been killed by a drunk driver.

In retrospect, it appears that I was dismissed from the jury because I am a chemist/scientist.  Despite not being selected, my jury summons provided a thought provoking experience and left me with several questions. I will now pose these questions to you, my fellow members of the scientific community.

1) Could you convict someone of a crime knowing that it is based on incorrect testimony?

2) We have spent years training our brains to critically analyze everything we think and hear. Can you shut that off on request?

3) In a system where those who testify swear under oath to tell the truth, is it hypocritical to expect those making the decision to suppress what they know to be true?

4) Why wouldn’t you want additional expertise on a panel of individuals deciding the outcome of a trial? Aren’t they the most qualified and as a result most likely to make the correct decision?


  1. 1. No.
    2. Not really; certainly not in a court of law.
    3. Dunno.
    4. I suspect part of the problem is ascertaining whether or not your expertise is valid or not; better to just throw it all out?

  2. I’ve practically begged to get thrown off a jury by mentioning that I was a scientist, saying things like “scientific truth has a special meaning to me.” It doesn’t always work, although I think I skeeved out a prosecutor enough that I might have been tossed.

  3. So far, I’ve only got a jury duty summons once, and I was lucky enough to not even be called as a potential juror. Just several hours waiting around in a big room…

    However, the general consensus I’ve heard about juror selection is that if you’re well educated, and demonstrate that you can think critically, you’ll more than likely get tossed… So, good news for scientists not having to spend time at jury duty. Questionable news for the US legal system.

  4. In my humble opinion, being able to think critically, which should be the goal of ALL scientists, is not considered a good attribute in a juror setting. If we, as scientists, are able to discover a place of mystery in our direct course of investigation, I would hope we all would want to investigate it further in order to reaffirm or dismiss our initial findings. To question the validity of statements made in the law profession that are believed to be definitive corrodes the judicial structure, and thus, all scientists should be barred from the juror role. However, if something is against the law it does not make it applicable to a guilty verdict. The classic example is the appeal of Prohibition in the early 1900s of America. The power of the lone dissenting juror is incredible, and because you have “strong” views about something does not mean you should affirm that you do. If you have these “strong” views because of analysis of the facts rather than a personal prejudice, I personally think it is your duty to not inform the trial members of your bias due to the fact that you are a rational, thinking, informed individual. “An Essay By The Trial By Jury” by Lysander Spooner is an interseting read.

  5. That’s funny, because I just had a jury duty summons last week. We learned in the training video, though, that we should really call it jury service though, because as citizens, we are performing a service to our community…

    We got there at 8:15, waited outside the building til 8:30 when it was unlocked. Waited around in the jury pool room til 9:30, watched the training video and about 30ish jurors were taken to some criminal trial (not me). Waited til noon, when we were told we had a 2 1/2 hour lunch break. Got back at 2:30. Waited til 3:30 when we were told we wouldn’t be needed and we could go home. Very boring.

    I agree that critical thinking and an inquiring mind is an important asset for a juror. Em talked about discovering mystery in the course of investigation and investigating further. Hopefully for everything a juror notices out of the ordinary, the lawyer notices three more. That’s really the lawyers job to find flaws and alert the jurors to inconsistencies in testimonial facts.

    It would be very hard for me to turn off my knowledge and I would be very hesitant to convict on knowingly incorrect testimony.

  6. I have been exempted from Jury duty because I was an EMT. What I find interesting in situations like this, is that a jury is supposed to be a group of my “peers” but as you have expressed, and I have seen before, the selection process does not choose our peers.

    Sad situation when all our legal system wants are sheeple, ready to believe every word presented to them by the “experts” without question.

    Carrie (Biochemist, volunteer EMT)

  7. To say to a juror you should forget everything you ever learned is plain stupid, and hopefully is corrected one day in the legal system. A jury trial is suppose to be amongst 12 peers. However, if there is a scientist in the jury who has technical knowledge that juror will bias everyone during deliberations; so in that respect I wouldn’t think it is proper to have scientists in the jury pool.

  8. The question “can you leave any expertise at the door” is both unconstitutional and barring you for saying “no” is also. It’s also obviously impossible to achieve and stupid to even ask it.

    Jurors are not restricted in any way, shape or form to any particular method or means of deciding – you only need to be a peer (people or citizen) of the defendent – as in “jury of one’s peers”.

    The reasons: first the Constitution, and second the US Supreme Court validated right to ‘jury nullification’. You don’t have to follow specific instructions like “checking expertise at the door”. The court has upheld verdicts made by nullification as being just as valid as any other.

    Judges and attorneys will insist (even in court) that you have no right to nullification, but you simply do and they are lying if they say otherwise. This is simply a usurpation of authority (beyond their legally defined authorities and rights for them) and nothing but power/ego/control trip. These folks simply want to be able to use rhetoric and the most abusive forms of rhetorical combat to decide all cases rather than empirical fact, law of physics or situational fact.

    Any rational person quickly finds that the criminal justice system has very little to do with justice – it’s become about “process” rather than justice in too many cases. Most convictions are on the skimpiest threads of logic and fact – it’s horrifying, frightening and immoral.

    It turns out that most people with an scientific or engineering backgrounds are the first to be summarily eliminated from jury pools and the mostly likely to cause legitimate hung juries because of piss-poor case fact and logic.

    On the other hand, if lawyer and judges had the skills of logic and fact validation that empirical rationalism requires, they probably would have become scientists and engineers instead – so it may a self-selecting and self-perpetuating system of abuse we can’t easily escape from.

  9. “The court has upheld verdicts made by nullification as being just as valid as any other.” JG

    There are several examples of cases where a juror was excused for mentioning/discussing jury nullification.

    Quoting this article from 2001:

    “Monday’s decision, however, is likely to deter nullification because a new jury instruction requires jurors to inform the judge whenever a fellow panelist appears to be deciding a case based on his or her dislike of a law.” said Deputy Atty. Gen. Karl S. Mayer.

    I don’t understand the intricacies of the ruling but it appears the defense in my selection process was trying to preemptively prevent discussions like this from happening.

  10. How did the other potential jurors answer #2?? Were they even asked?? I’m absolutely appalled.

  11. I’ve read some comments, too lazy and drunk to read the rest. I agree with some above people though, why would a jury not want people who pride themselves in thinking objectively, and have made it a base for their entire existence. I’d rather be tried by a jury of phD’s than a jury of illiterate retards who are too stupid to have their own ideas about anything.

  12. Crystallinity,

    I was the only one asked #2.

  13. But it was the defense attorney, not the prosecution, asking you those questions. He didn’t want a conviction based on false information, he wanted to bring in an expert to explain that the breathe tests were false and the machine not to be trusted, ergo his guy was innocent despite the breathalyzer results. He wanted to know if you could let a guilty man go based on false expertise, despite your knowledge to the contrary.

  14. This is quite disturbing. I would find it difficult to swallow patently false information and not let it impact my decision, especially given that someone’s life and honour are at stake.

    Really though, both prosecution and defense need to be good at picking jurors.

  15. Wow that’s so crazy the same thing happen to me a few years back..They had also asked if anyone likes math and I was the only one who said yes..they asked me why and I said “math is one of the main foundation that all science is built upon including the BAC test..” I am also a chemist and did not get picked..they only want dumb people..

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