Impartiality is the key here. When you say "purge rate" I'm assuming you mean the metabolization of the alcohol sometimetimes referred to as the "burnoff rate"? The science of this particular case/scenario is a bit facinating.
The Burnoff rate/ Purge rate, although influenced by many factors, is generally averaged to be @ about .015% per hour. In this scenario the patient was tested 3hours & 45 min. later. The new numbers were 157mg/dl. After doing the math you find that this patient had a Burnoff/metabolization/Purge rate very near twice the considered avg.
Do "we" have an "accepted avg." when it comes to absortion rates?
Your 157 mg/dl level would equate to about .133 BAC. So, if we assume that the subject went from about .226 to .133 in 3 hours, I would agree that the absorption rate over three hours would be about double the average. But, there are other factors that might come into play with the testing of plasma versus whole blood - and the equation can be off by as high as 25% in some cases.
And, no, there is no accepted average absorption rate because there are to many variables, and it can be so extreme as to cause death if consumed in a short period of time. The purge rate is generally between .010 and .015 per hours.
So, who are you in this situation and what is your legal question? No matter how you slice it, the person was still WELL over the
per se limit ... though making a case for DUI if he was nearly an hour away from the car and had been drinking at home before the arrest is going to be tough.
If you are the driver, consult legal counsel.