Prosecutorial Error With State's Last Witness Creates Grounds for Possible Mistrial in Chauvin Trial

Earlier today, the defense rested in the murder trial of former Minneapolis Police Officer Derek Chauvin, charged in connection with the in-custody death of George Floyd.


Chauvin waived his right to testify on his own behalf, asserting his Fifth Amendment right to remain silent during the course of the trial.  That was not a surprising development.

But what came next was quite surprising, and potentially a critical moment in the case for the prosecution.

The prosecution advised the Court that it would have one rebuttal witness.  A rebuttal witness can be called to present testimony in response to evidence heard for the first time during the defense case.  As is very common, the rebuttal testimony would come from one expert witness who previously testified, Dr. Martin Tobin, and the testimony would be in response to testimony given by a defense expert.

But the surprising part of the prosecution’s announcement was that it intended to have Dr. Tobin testify about newly discovered evidence — a Hennepin County Medical Examiner report on the level of carbon monoxide (CO) in the blood gas testing of arterial blood drawn from Floyd at the hospital.

The standard panel of blood gas readings sent at the request of the ER physicians would not normally have included this test result.  The machine that tests the blood does measure the CO content, and it is reflected in the master report that is produced by the machine, but that reading is not normally sent to the ER where the patient is being treated. The Medical Examiner didn’t ask for that particular test reading because he didn’t deem it relevant upon examination.  So the test reading was reflected in the hospital records all along, but it had never been noted by anyone until the Medical Examiner, Dr. Baker, went back to the records after hearing some of the earlier expert testimony in the case.


Even though the report has been in existence since the night of Floyd’s death, the prosecution claimed it first received it yesterday by Dr. Baker.  The report’s findings would have supported earlier testimony by Dr. Tobin and undermined the testimony of the defense expert, Dr. Fowler.

The bigger problem for the defense what that Dr. Fowler has already left Minneapolis and was on a plane returning to his home — meaning the defense would be unable to call Dr. Fowler back to the witness stand after Dr. Tobin in order to have Dr. Fowler review the same testing reports and incorporate them into this previously testified opinion.  The impression that would leave the jury with would be that Dr. Fowler was not able to address the criticisms that Dr. Tobin was likely to testify to as a rebuttal witness using these test reports that had never been sent to the defense in the case. Had the reports been timely produced to the defense as required, Dr. Fowler would have had the test reports to review at the time he formed his opinions and prepared his testimony.

Judge Cahill sustained the defense’s objection to the prosecution request to have Dr. Tobin testify about the CO test results, or to criticize Dr. Fowler’s testimony based on information in those reports.  Judge Cahill did allow the prosecution to call Dr. Tobin to testify in response to other topics addressed by Dr. Fowler in his testimony on behalf of Chauvin.


It is not completely clear to me at this point, but there seems to be an issue involved with regard to Floyd laying next to the exhaust on the police vehicle — with the motor running?  The CO coming from the exhaust and/or other environmental factors being a possible cause for the lack of oxygen in his lungs as CO binds with hemoglobin in the blood and prevents oxygen from binding.  Dr. Fowler’s report back in February noted a lack of testing on the part of the hospital regarding blood CO, giving the prosecution at least 60 days notice that he would testify on that issue.  Had the test results been provided prior to the trial, Dr. Fowler’s testimony would have been different.  Dr. Tobin’s intended testimony was that such testing had been done, and CO was ruled out as a contributing cause by the blood gas results — undermining Dr. Fowler in an unfair and prejudicial manner since the prosecution had the evidence all along but did not provide it.

Judge Cahill warned the prosecution that even if Dr. Tobin’s testimony “hints at” the existence of the testing results the prosecution would be at serious risk of having a mistrial declared.

When Dr. Tobin took the stand, the prosecutor began a series of questions about Dr. Fowler’s report — which Dr. Fowler had testified to, and which had been admitted into evidence.


The prosecutor asked about one part of the Fowler report which said it was possible that Floyd’s CO level in his blood could have been as high as 15-18% — meaning it was the presence of CO in his blood and not the actions of Chauvin and the officers that led to the “low oxygen” level that killed Floyd.  Dr. Tobin testified that he disagreed with that opinion.


The prosecutor then asked, “Why?”


The defense objected and asked for a “sidebar” discussion with the Judge where I’m certain Defense counsel Nelson asked for a mistrial.  The content of the sidebar is unknown, but after it was done the Judge sustained the objection and directed the prosecutor to rephrase the question.

The prosecution asked again about whether Dr. Tobin agreed or disagreed with the opinion that Floyd’s CO level could have been as high as 18%, and Tobin again testified that based on his review of blood testing done at the hospital, Floyd’s oxygenation rate in his blood was 98%, and since the combination of O2 rate and CO rate must add up to 100%, the only conclusion is that the CO rate was only 2% –based on the testing.

How this is not a direct violation of the limitation set by Judge Cahill is a mystery.  The Judge and defense counsel went behind closed doors — likely so the defense counsel could make a proffer about what his experts MIGHT say in response — holding open the potential that the Court might recess the trial long enough for Nelson to get the defense expert back to testify.

But ultimately that did not happen.  Dr. Tobin’s rebuttal testimony ended, the prosecution said it had no further witnesses, and Court adjourned for the day.


To be continued.

[Author’s Note:  The original version of this story referenced “carbon dioxide” and not “carbon monoxide” as the blood gas at issue.  The story was drafted with a bit of haste as this was a “breaking” news matter, and I was away from my computer when the story first published and unable to make the correction when it was noticed.  A RedState Editor made the necessary changes to the article’s content to correctly reflect the matter at issue in the trial as reported.  I apologize for the error.]


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