Regarding Dr. Shewmon's philosophies, it's my opinion that he would consider any patient with a beating heart who meets brain death criteria to be an "alive organism". He does not consider the brain to be important in the philosophical discussion of "alive"-- if the body functions with somatic support (ventilator, provision of IV or enteral fluids and nutrition), then he considers the organism alive. He leaves the determination of whether that organism is a human person to others.
He would perhaps answer that he does not need to examine Jahi to determine, within his philosophy, that she is "alive", as long as her body functions on a ventilator with other nutrition and fluids for support.
Read this link carefully-- it is as close to sitting down with a cup of coffee and having discussion with Dr. Shewmon as we can get.
https://bioethicsarchive.georgetown.edu/pcbe/transcripts/nov07/session5.html
He recognizes that humans enact laws regarding determination of death, and brain death. He clearly realizes that all kinds of people without any brain function meet the legal criteria of "alive" or "dead" based upon the laws where they live. His is a purely philosophical argument based on science-- not a religious one. If the organism is capable of any kind of functioning, it is "alive" in his philosophy. I daresay that he would even consider a person with no brain function and an artificial heart, or on cardiopulmonary bypass, "alive", if any aspect of the rest of the body was able to function with the support of the artificial heart or bypass machine. He might even consider a decapitated body alive, if it was possible to provide ventilator support and nutrition, and the body continued to function. For him, if I understand his philosophy correctly, "life" is all about the functioning of cells, and organ systems-- if they function at all, they are "alive". Alive as in "an organism."
So, it may not matter to him if SPECT is not sensitive enough, or EEG brain waves are weak, nonexistent, or present-- if any aspect of the intact corpus (body) functions, to him that equals "alive". I think that's why he was willing to put forth his affidavit to the court without doing an exam in person of Jahi. Jahi is "alive" enough for his philosophy to consider her "alive."
Now, legal definitions of brain death are a whole nother conversation, especially as the definitions of alive and dead affect eligibility for government support and other monies. He recognizes Jahi is dead under the laws of California and the UDDA. I think he also knows it's pretty unlikely those laws will change anytime soon. So, he's focusing on little technicalities in Jahi's case that are contrary to typical death criteria, to attempt to persuade the courts that she no longer meets the California definition of brain dead. That's how I read it.
I actually don't think the courts will ultimately reverse the determination of death for Jahi, but it will be interesting to watch how this plays out. It is a fascinating philosophical discussion, especially with religion left out of the discussion. Especially what it means to be "human" vs what it means to be an "organism". Quite fascinating, IMO.