Claiming that someone who died before covid started, somehow said PCR was not reliable for covid - neither credible, nor useful
You are mistaken. Nobody is saying that Dr. Kary Mullis was talking about
the Covid-19 virus. Mullis died in August, 2019. The video is saying it was The University of Oxford Center for Evidence Based Medicine and The University of the West of England that found the PCR test can produce false positives.
However, at approximately the 12 minute mark, this video quotes Dr. Kary Mullis in 1993 as saying that the PCR was being improperly used by researchers to estimate free viral mRNAs.