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Posted on April 16, 2021 by in The Law of Self Defense

Andrew Branca: Chauvin Trial Day 14 Wrap-Up

Andrew’s commentary and opinions do not reflect or represent CCW Safe. They are his own and we are presenting the coverage because this trial could be of interest to our members and to generate thought and discussion.  

Chauvin Trial Day 14 Wrap-Up: Mistrial Narrowly Avoided, Closing Arguments Monday

Defense offered no practicable opportunity to contest Dr. Tobin’s rebuttal testimony

Welcome to our ongoing coverage of the Minnesota murder trial of Derek Chauvin, over the in-custody death of George Floyd.  I am Attorney Andrew Branca for Law of Self Defense.



Today was mercifully brief in duration, but packed full of action—at least, for certain lawyer values of “action,” so let’s dive right in.

Two notable events I’ve already discussed in a breaking news post was the decision of the defense to call no further witnesses—and this included waiving the prospect of having Chauvin appear as a witness to testify on his own behalf.

Chauvin elected to assert his 5A right to not testify, and when offered to have the jury instructed that guilt could not be inferred from his not testifying, he affirmed he wanted that instruction given.  You can see my previous write-up of those events, including court room video of that discussion and exchange, here:

BREAKING: Derek Chauvin Will Not Testify, Asserts 5A Privilege

The big surprise of the day, however, was the state’s sudden claim that they had discovered “new evidence” that justified re-calling state expert witness Dr. Martin Tobin, pulmonologist, to the witness stand to rebut some of yesterday’s testimony by defense expert Dr. David Fowler, a forensic pathologist.

The “new evidence” was purportedly just-discovered data on Floyd’s blood oxygen levels when at the Hennepin County Medical Center.

The state wished to have Dr. Tobin testify about that data to rebut suggestions by Dr. Fowler that given the proximity of Floyd’s face to the exhaust of squad car 320, it was possible that Floyd’s carbon monoxide blood concentration could have been as high as 18%–a level Fowler testified was sufficient to be dangerous to Floyd, and a contributing cause to Floyd’s death, given Floyd’s fragile physiology.

As these things tend to go in court, the argument over whether to allow Tobin to be re-called as a witness for this rebuttal purpose took about twice as long as did his actual testimony—but for good reason.

Obviously, this demand for rebuttal by the state, particular on this blood data “discovered” just after Fowler’s testimony ended yesterday afternoon, and with notice provided to the defense only about 5 o’clock in the evening, was about as late in the course of the trial as could be imagined.

Further, the defense expert witness on this subject matter, Dr. Fowler, was presently on a plane flying home while the state was arguing in court for their own expert, Dr. Tobin, to be recalled.

During the discussion about whether Tobin should be permitted to provide additional testimony, the state set out four areas that they wished Tobin to testify about.

First, the state claimed that the Hennepin County Medical Examiner, Dr. Thomas Baker, after hearing Fowler’s testimony yesterday on the carbon dioxide issue, had somehow dug into the hospital’s records and found that Floyd’s blood concentration of CO had, in fact, been measured at the time—but had never been previously produced when the parties had subpoenaed Floyd’s medical records.

The state now wanted these data to be shared with the jury and explained by Dr. Tobin, to rebut Fowler’s claim that Floyd’s CO concentration could have been as high as 18%.

Normally, of course, the state would have been expected to make such arguments in Dr. Tobin’s original testimony, and their failure to do so would not be a good reason to suddenly allow Tobin to re-testify now.

An exception to that normal prohibition on re-testimony, however, can be made if the defense itself had “ambushed” the prosecution with scientific arguments for which they had not provided the state with notice.

Prosecutor Blackwell argued that Fowler’s reference to CO concentrations as high as 18% had never previously been disclosed to the state, and so qualified as just such an “ambush” that justified Tobin’s re-call to the witness stand.

The defense countered that Fowler had explicitly referenced CO as a possible contributor to Floyd’s death in his expert report shared with the state weeks before trial began and had even recommend that the state test the blood for CO concentration.

It was only the state, not the defense, that had possession of the blood.  As a result, the state was on notice with respect to the CO issue, and if they failed to address that issue in a timely manner, that was on them.

Judge Cahill agreed with the defense with respect to this “newly discovered” blood gas level data, and informed the state that if Tobin so much as hinted at this new data, the Judge would order a mistrial had occurred.

That said, Cahill said he would allow Tobin to speak to the CO concentration issue if he only referenced data that had long been available to both parties.  That opened the door to the prosecution having Tobin reference Floyd’s oxygen (rather than carbon monoxide) levels, and use the O level to infer possible CO level.

This is possible because O and CO both compete for the same binding location on hemoglobin, and only one of them can bind any particular hemoglobin protein.  So, a protein bound by O cannot also be available to be bound by CO, and the reverse.

Because the parties were aware that blood gas measurements had indicated that Floyd’s blood had O levels of 98%, it could be inferred that his CO levels could be no greater than the remaining 2%, which was well within normal.

There was also another entirely separate issue that the state also wanted Tobin to provide rebuttal testimony on, and this involved Fowler’s claim yesterday that he had been unable to find any scientific studies supporting Tobin’s earlier claim that the hypopharynx could be narrowed by pressure placed on a person’s back.  Fowler said he had searched the major scientific publication database, known as PubMed, and come up with no results.

The state claimed that Fowler’s reference to this PubMed search was “new evidence” not previously shared with them, again qualifying as “ambush” testimony, and again providing the exception necessary for them to have Dr. Tobin testify on this issue on rebuttal.  The state indicated that Tobin would testify that there were, in fact, a number of scientific papers and studies that supported his claim.

Naturally the defense objected, saying that they would not have any opportunity to research Tobin’s claim of such papers and studies existing, much less of actually reading these materials in order to understand if they supported Tobin’s claim or were subject to effective impeachment.  Further, again, the defense expert witness Fowler was on a plane and not available to the court.

Judge Cahill ruled that Tobin would be permitted to testify as to the existence of such papers on rebuttal, in a summary fashion.   

The state also wanted to be permitted to have Dr. Tobin testify again on his earlier claim that the cause of Floyd’s death was hypoxia, or low oxygen, claiming that Dr. Fowler had contested that claim in yesterday’s testimony.

Fowler had claimed that it wasn’t low oxygen induced by positional asphyxia that caused Floyd’s heart to fail, as Tobin had argued, but rather that it was Floyd’s heart failing that had resulted in a low oxygen state.

This was the weakest argument for rebuttal testimony offered by the state.  Really, both Tobin and Fowler agreed that Floyd had evidenced a low oxygen state by various symptoms, such as a particular convulsive leg kick.

Their only disagreement was the precise mechanism that had led to that low oxygen state—Tobin claimed positional asphyxia as the cause, and Fowler claimed cardiac arrest as the cause.

Cahill ruled that Tobin would not be permitted to testify as to this issue on rebuttal.

So, in the end, Tobin was permitted to speak to the issue of inferring a maximum CO concentration in Floyd’s blood of no more than 2% based on the measured O level of 98%, and to inform the jury that he was aware of some 12 to 20 scientific papers that supported the notion that smaller lung volume resulted in a narrowing of the hypopharynx.   

Here is that discussion among the parties and Judge Cahill:

State Direct Questioning of Tobin Rebuttal

That direct questioning on rebuttal was conducted by Prosecutor Blackwell and took only about 8 minutes.  Excitement, of the legal type, occurred about four minutes into direct when Tobin appeared to reference the blood gas data that Cahill had cautioned would result in a mistrial.

Nelson immediately objected, and the court went into a couple of minutes of sidebar, during which I’m sure the defense was asking for a mistrial.

Frankly, in my professional opinion, a mistrial in this case would be entirely warranted, if not from this particular incident in isolation, then from the accumulated harms done to the defense by the state’s untimely dropping of thousands of exhibits on the defense even as the trial proper was taking place, averaging nearly 500 new exhibits each day of the trial.

At the end of that sidebar, however, Blackwell returned to continue his direct of Tobin, so no mistrial, and presumably he was cautioned to avoid mention of the prohibited blood gas data.

Defense Cross-Examination of Tobin Rebuttal

After Tobin’s rebuttal testimony on direct, there was another lengthy pause in the proceedings, conducted off microphone (and perhaps even in the judge’s chambers rather than in the court room), during which I’m confident that Nelson was once again arguing for a mistrial.

Apparently that argument was to no avail, however, because Nelson did return and conduct cross-examination of Tobin.

Without any real way to prepare for this unexpected testimony, there really wasn’t much he could accomplish.  As a natural consequence of this constraint, his cross took only about two minutes, and you can view that here:

That ended Tobin’s rebuttal testimony.

Judge Advises Jury to Expect Closing & Deliberations Monday

At this point the state and defense both made the final announcement that they were resting their case in chief, and Judge Cahill turned his attention to the jury.

They would be dismissed for the day, and until Monday at 9:00am CT, at which time they would return to court to hear the closing arguments of the state and the defense, receive their jury instructions, and begin their deliberations.  They were reminded that they were to be sequestered during deliberations, and so were cautioned to “pack a bag.”

On the topic of how much to pack, Cahill suggested that they plan for a long sequestration, and hope it turns out to be a short one, but that ultimately only the jury could decide how long deliberations would take.

The jury was then dismissed.

Discussion re: Charging Conference (Jury Instructions)

After the jury had left, there was a brief discussion about the charge conference for this trial.  The charge conference is where the parties meet with the judge to iron out the precise jury instructions to be given to the jury to guide them in their deliberations.

Obviously, because those instructions guide the jury to either a guilty or not guilty verdict, each party has an interest in trying to bias those instructions in their own favor, both by ensuring that particular desirable instructions are included among those given to the jury, as well as that any customization of the instructions be favorable to their own interests.

Minnesota, like most states, has standardized jury instructions for criminal trials, but standardized instructions are always subject to some customization by a trial judge to best fit the particular facts and legal arguments in a given trial.

I’ve covered the relevant standardized jury instructions likely in this case in a blog post early this week, here:

LIVE: Chauvin Trial Day 12 – Meet the Jury Instructions, Bring On The Defense Case

The selection of the specific instructions to be given to the jury, and discussion of any possible customization of those instructions, are what is hashed out during the charge conference.

Unfortunately for us, Cahill announced that the charge conference in this case will take place in chambers, so will not be subject to observation.  I do expect we will be able to observe the actual reading of the instructions to the jury in court on Monday, however, and if I obtain physical copies of those final jury instructions, I’ll share them, as well.

And that wraps up our coverage of the Chauvin trial for today, folks. Expect to see us back with live coverage of the court’s proceedings on Monday morning, and perhaps a post to carry us over the weekend if some interesting topic strikes my fancy in the interim.

Course Special: Lawful Defense Against Rioters, Looters, and Arsonists

Before I go, in view of the ongoing riots raging presently in Minneapolis, and likely to explode across the nation when this case arrives at a verdict (or mistrial), I’ve also taken the liberty of putting together a special opportunity to access our best-selling course, “Lawful Defense Against Rioters, Looters, and Arsonists,” available in both online streamed and DVD formats.  You can learn more about that course, by clicking here.

And thanks, as always, to both Legal Insurrection and CCW Safe for the support that makes my coverage of this case possible.


Attorney Andrew F. Branca

Law of Self Defense LLC


Attorney Andrew F. Branca’s legal practice has specialized exclusively in use-of-force law for thirty years.  Andrew provides use-of-force legal consultancy services to attorneys across the country, as well as near-daily use-of-force law insight, expertise, and education to lawyers and non-lawyers alike in the form of blog posts, video, and podcasts, through the Law of Self Defense Membership.