I am a British writer trying to get law enforcement procedure right in a thriller set in San Diego, CA. (There are numerous plot reasons that prevent me placing this action in e.g. the UK where I am slightly less ignorant about the law and law enforcement.)
The question is, given the following circumstances, who can search the dead man's residence, and on what basis?
The hypothetical situation: a man has died in an incident at work - whether it is an accident, homicide, or what we call in the UK manslaughter (which is to say death incidental to other action and without intent...) is unknown at the time law enforcement would like to perform the search (partly in hope of discovering whether a crime has in fact been committed).
The man is reasonably believed to be in (legitimate) possession information concerning a threat to US National Security. Because of the national security issue, the FBI are involved in a counter-intelligence role. The information may be on computers/devices in the man's home.
There is no evidence per se that the man's death was due to sabotage, but there is prima facie evidence of unauthorised interference with the employer's computer systems, which might have caused the man's death.
I cannot find any basis for a warrantless search of the man's residence based on his death alone (having reviewed various sources including California Code, Government Code - GOV § 27491.3, 4th Amendment and some commentary on related Supreme Court decisions), given that he died at work.
His sole living relative (daughter) does not reside at the property. She does however have a key and might therefore be considered "in control" of it. (But if so, would she have to enter the property first?)
Questions: Is a warrant required/advisable to search the man's home, or could the daughter be asked to permit entry? If a warrant is required, who would apply for it? UCSD PD or FBI, and on what basis?