Judge Peter Cahill threatened to call a mistrial in Minnesota’s case against former Minneapolis Police Officer Derek Chauvin Wednesday after prosecutors tried to introduce additional evidence last-minute. State prosecutors called Dr. Martin Tobin to testify a second time in the trial as a rebuttal witness to Dr. David Fowler, a witness for the defense on Wednesday, according to the Star-Tribune. During his testimony, Fowler had posited that carbon monoxide from a nearby police vehicle potentially played a role in the death of George Floyd. Tobin disagreed with Fowler’s analysis that Floyd’s blood was saturated 10-18% with carbon monoxide. Tobin said Floyd’s blood was 98% saturated with oxygen, leaving only 0-2% left for carbon monoxide. As part of his rebuttal, Tobin intended to point to Floyd’s blood test results that measured the concentration of carbon monoxide. Cahill shot down the prosecution’s attempt to introduce the test results as evidence last-minute after an objection from Chauvin’s defense attorney, Eric Nelson.