The crap that sometimes comes out of the Department of Morons & Villains is often best exemplified by virtue of the ridiculous fact that the HO (Hearing Officer)acts as both prosecutor and judge.
That would be kind of like if someone wanted to be Jack Kevorkian only because they were also the mortician.
It gets worse; it's also like if they own the cemetary.
As unfair as it is, she or he can legally object to your evidence, rule on her or his own objection, decide against your California DMV lawyer, and admit or not admit either party's evidence which means admit DMV's evidence but deny any weight to driver's evidence.
That's not the end of it. Your attorney can still win.
That's because the California Driver Safety Officer offers evidence in the form of documents and/or witnesses.
The San Diego Hearing Officer usually goes with the DUI police report, DMV records, DUI alcohol reports and the important DUI officer's problematic sworn statement called a "DS 367."
A DUI lawyer's strategies & approaches at the DMV hearing are technical.
California DUI / DMV proof problems are bases for not affirming a suspension.