So what he saying is:
AK enzymes have nothing to do with blood groups and so the Bamber statement that the presence of AK1 meant that the blood was group A is gibberish.
Rabbit AK is detectably different from human AK, and he'd be surprised if a scientist would make that mistake, so the assertion that rabbit blood could have provided the AK1 enzyme said to be from Sheila is extremely unlikely.
One of the reasons the evidence that Sheila's DNA* was in the silencer was rejected by the court of appeal was because no one could give a statistical evaluation of the likelihood that a match of 17 bands out of 20 bands of DNA tested in both samples meant that the DNA came from a closely related person. There is now a statistical method for calculating those chances.
He criticises the CCRC for underestimating the possiblity of contamination being the source of Sheila's DNA in the silencer and also, it appears, for not recognising the significant fact that no blood was detected in tests immediately prior to the DNA tests being undertaken (because it had been swabbed out for blood grouping tests).
He appears to be saying that he just did his job, and the CCRC ended up scoring an own goal for Bamber.
* For those less familiar with the sequence of the DNA testing, at the time the CCRC referred the case for appeal the test results had concluded that DNA found in the silencer did NOT match Sheila's. Further tests were undertaken in the time between referral and appeal and DNA matching 17 out of 20 bands for Sheila's natural mother was found.