Legal Question in Real Estate Law in California

Unless she is the owner, a deed from your sister is of no value. If tyour mother decides to sign a deed she can give the home to anyone she wants to. Is your mother competent? Does she know what she is doing? Are you suspicious of some type of undue influence. These are all thisng you may want to discuss with counsel.

Of course not. Only the title holder / owner can 'deed' the property to someone else. That means your mother would have to 'deed' it to the sister, but she can do so 'legally'

only if she is mentally competent and not under duress or undue influence. It sounds like possible improper behavior and elder abuse/fraud that should be investigated. If serious about hiring counsel to help in this, and if this is in SoCal courts, feel free to contact me.

I'm more inclined to go with Mr. Nelson's answer. The correct answer depends upon whether the sister has any authority to execute a deed to transfer property of which she isn't the owner. Usually, one cannot transfer someone else's property, period. Remember the old saying, "He who sells what isn't his'n, must buy it back or go to prison." However, in some cases, another person is cloaked with legal authority to manage the affairs or deal with someone's property. This can be done via a properly-executed power of attorney, or by a court-approved and court-supervised conservatorship. You don't tell us whether your sister was acting as a conservator or under a power of attorney. This could be controlling on whether the making of the deed was proper or a fraud.