Regarding the Supreme Court decision in People v Hartwick and People v Tuttle, I offer the following agreement that might be used between any patient and any caregiver. Both can benefit from it under any circumstance. It costs nothing but time, ink, and paper, and offers added protection in the event you are arrested and tried for marijuana use if and when you need it. You can find the ruling in Tut/Wick here: http://courts.mi.gov...71 Opinion.pdf. Footnotes 77 and 78 lay out the case that this type of documentation is admissible, and even necessary, evidence in any prosecution regarding marijuana.
The agreement's tenets were used in the successful defense in State v Steven Fisher (http://komornlaw.com...n-8-opinion.pdf). He was found to have possessed a reasonable amount more than thirty pounds and in compliance with the other elements of the required defense.  It is not useful to only registered patients and caregivers, but also provides what the courts require as prima facie evidence in non registered sec. 8 defenses. Any patient or other person, registered or unregistered, can qualify as a caregiver under the definition found in the law (sec. 3(k)) to any patient, registered or unregistered, with or without connection through the registry per the definitions found in sec. 3 of the MMA. There are no limits on the number of patients a caregiver can provide for nor caregivers a patient can have in sec. 8. Police officers and informants who enter into it are not able to entrap medical users.
Please note that the agreement covers two of three necessary elements of the Affirmative Defense found in sec. 8 of the law, i.e., that you and your doctor have met and concluded a bona fide medical exam and you have been certified to use marijuana, and that patients and caregivers are engaged in medical use to treat or alleviate a patient's condition or symptoms. The third element is to adhere to the requirement that an amount not more than necessary is held in possession. I have suggested that twelve oz is an amount not more than necessary to supply a patient who uses a zip a month for a year, and would welcome any reasonable argument otherwise. To this point I have had no takers.  It also intends to prevent the need to have a physician testify, which is not advised except if necessary to provide evidence at trial, saving time, trouble, and expense. Furthermore, it is best not to have any witness for the defense questioned by a prosecutor for obvious reasons. It intends to establish the required prima facie evidence of a bona fide physician patient relationship without a physician present. It will be necessary to require your physician to sign his or her proof found in the supporting documents. If not, the court ruled that the actual text of the physician statement submitted as part of the registration process might suffice. Registry cards do not. It would nonetheless be best to have both registration and this or a similar written agreement. The agreement requires notarization. Your bank provides notary services to its customers free. Many physician offices have a notary on their office staff, and all attorneys have a notary on board. It is admissible under the Michigan Rules of Evidence as self authenticating notarized evidence (MRE Rule 902 (8)) and self authenticating Certified Records of Regularly Conducted Activity (MRE Rule 803 (6) and MRE Rule 902 (11)). 
You will do well to ask an attorney re: any legal questions. I am not an attorney and have no professional relationship with anyone in that regard. It is my own work as informed musing if nothing else. It is not intended as legal advice. If anyone should want the added protection, something like this might be used in consultation with a trained attorney. I have no objection to anyone using it verbatim or edited. It, by itself, provides no protection from arrest and due process as sec. 4 state registration does.
 
 
Patient/Caregiver Agreement to Engage in the Medical Use of Marijuana
 I,______________________________________, swear and affirm that I am a patient under the Michigan Medical Marihuana Act, MCL Initiated Law 1 of 2008.
Dr._____________________________, a physician authorized under Part 170 of the public health code, 1978 PA 368, MCL 333.17001 to 333.17084, or an osteopathic physician under Part 175 of the public health code, 1978 PA 368, MCL 333.17501 to 333.17556, physician license I.D. number____________________ , has stated that in the physician's professional opinion, on or about (date)___________________________, and after having completed a full assessment of the patient's medical history and current medical condition made in the course of a bona fide physician-patient relationship, that I am likely to receive therapeutic or palliative benefit from the medical use of marijuana to treat or alleviate a debilitating medical condition or symptoms associated with the debilitating medical condition (copy attached) .
 I hereby designate_______________________________ as my caregiver under that law, and agree to conform to the Act in the medical use of marijuana to treat or alleviate a debilitating medical condition or symptoms associated with the debilitating medical condition
 I, ______________________________________(caregiver), swear and affirm that I am at least 21 years of age and have agreed to assist with the above named patient's medical use of marijuana in accordance with that law to treat or alleviate a debilitating medical condition or symptoms associated with the debilitating medical condition. I have not been convicted of any felony within the past 10 years and have never been convicted of a felony involving illegal drugs or a felony that is an assaultive crime as defined in section 9a of chapter X of the code of criminal procedure, 1927 PA 175, MCL 770.9a.
 Confidentiality: Each party agrees and undertakes that it shall not, without first obtaining the written consent of the other, disclose or make available to any person, reproduce or transmit in any manner or use (directly or indirectly) for its own benefit or the benefit of others, any Confidential Information, save and except that both parties may disclose any Confidential Information to their legal advisers and counselors for the specific purposes contemplated by this agreement. Presentment or disclosure of this information is not prohibited as required by law or in any prosecution pertaining to the medical use of marijuana.
Subscribed and sworn before me this date: ____________________________
 Patient sign here: _________________________________
 Subscribed and sworn before me this date: ____________________________
 Caregiver sign here: ________________________________
 /s/_________________________________
 Print Notary Name: ________________________________
 Notary public, State of Michigan, County of _____________________
 My commission expires ___________________
 Acting in the County of ___________________
 
 
DO NOT OVERLOOK the supporting documents. Use one or the other: https://sites.google...attredirects=0, which requires notarization, or https://sites.google...?attredirects=0, which does not.