How can you access a computer that has been password protected after death?

Which password, user or firmware?

Password protected how? Are you just referring to a login password or an account's admin password?

Without proof that you legally have the right to access the Mac Apple can not tell whether they should help. There are published (by Apple) methods to reset the user account passwords without knowing what they are by using Recovery mode.

Depending on the version of operating system and the level of protection afforded the

main user admin account, or perhaps the whole hard drive (file vault or total encryption)

the effort may vary. Also, depending on the computer hardware build model, it may be

possible to get past some hardware entrenched security. Physical access to the Mac

and in some instances, changing the configuration of memory capacity, could be used

to help get past some kinds of secure block.

•Apple OS X Security Configuration Guides - Apple Support (.PDF)

https://www.apple.com/support/security/guides/

There are reasons why some items are harder to remove than others, if you are only

dealing with an Admin password, it may be possible to start the computer anyway

but from a retail install-restore DVD and access tools made available from the Installer.

•results of topic search: OS X reset admin password - google:

https://www.google.com/?gws_rd=ssl#q=OS+X+reset+admin+password

•Five Ways to reset a Lost Admin Password - tidBiTs:

http://tidbits.com/article/14437

There is a way to reset the Admin password from the Installer DVD. Then boot the

computer from the hard drive (using another menu-bar choice within the Installer) so

as to return to running the Mac from its own hard disk drive version OS X. To re-set

the Admin password, is to replace the old one by this method, with one you create.

There are other method of perhaps making a new Admin account and then transfer

access to those existing older Admin account files to the new Admin account.

A command-line or single-user mode access may be possible, too; that implies a

startup into the terminal screen so commands to undercut the user interface may

be applied to the basic system beneath the visual OS X, then restart to see effect.

•How to reset your Admin Password - Yosemite 10.10 (and back to 10.8.5?)

http://www.macobserver.com/tmo/article/os-x-yosemite-how-to-reset-your-administr ator-password

Older OS X versions (Snow Leopard & earlier) see:

•OS X: Changing or resetting an account password (Snow Leopard and earlier) - Apple Support

Newer OS X versions (Lion 10.7 & Later) see:

•OS X: Changing or resetting an account password - Apple Support

There is a fair amount of reading. You may also consider an Apple authorized service

provider or Apple Store genius, but you may have to call ahead and also have proof

of the ownership has been transferred or of legal access to the deceased's property.

A manager may be able to help you if you end up doing this. Usually there is a fee

for someone to go into a computer and try to retrieve documents or attempt to access

files that are almost unreachable. Certain secure methods are almost impossible.

Sorry for not spelling out a simple method, not knowing the exact circumstances.

Good luck & happy computing! 🙂

PS: this reply started prior to any other replies