The California Administrative Procedure Act permits parties to use affidavits, declarations, and even letters in lieu of live testimony as evidence in an administrative hearing. This aspect is one of the big differences with civil litigation or criminal trial in that an unauthenticated document containing hearsay is permitted to be entered into evidence and carry the same weight in the administrative record as a witness testifying.
Even in the event the offering party fails to notice the opposing party of the use of the document in lieu of live testimony or fails to produce the actual witness to testify at the hearing if the opposing party indicates that it wishes to cross-examine, the administrative law judge is still required to take the document in as administrative hearsay. And although it alone cannot be used as the sole evidence to prove that which is started therein, it can be used to supplement or corroborate other forms of evidence.
However, one aspect that MUST be contained within the writing – whether an affidavit, declaration, or letter of support – is an acknowledgement that the author has read and understands the underlying action. Whether it is an Accusation, Statement of Issues, Temporary Suspension Order, Petition to Revoke Probation, etc., the author needs to know why the licensee or prospective licensee is proceeding to hearing. They have to know what wrongdoing has been alleged against them. Without that acknowledgment, the remainder of the content – i.e. evidence of rehabilitation, mitigation, or good character – loses almost all of its credibility and weight in the eyes of the adjudicator.
In practice, this is often a hurdle that has to be overcome by the party seeking to use the declaration. It means that they have to send a copy of an Accusation or other document that will detail allegations of misconduct or otherwise bad behavior that is often embarrassing if not outright disturbing. And that is regardless of whether what is being alleged is actually true. For example, if you have been wrongfully accused of a sexual assault, would the first thing you want to do is go to your employer, colleague, or clergy informing them of the false allegation and asking for their support? Most people would rather never have to communicate such a thing.
However, such is a minimum requirement in order to obtain the types of affidavits, declarations, and letters of support that can actually help a licensee at hearing.