How to access data on a locked iPhone 4 with Activation Lock without deleting the account?

Also note in the support article that Zachyy provided, Apple will not be able to get into the device because they do not know the Passcode either, and there is no backdoor access to bypass the Passcode. Apple can give you access to the Apple Account with the proper documentation and you may be able to see data that was stored in iCloud if that was used. You will not be able to get into the device though and view any data stored there.

While we may also be able to help remove Activation Lock from devices that use your loved one’s original Apple Account, their iPhone, iPod, and iPad will need to be restored to factory settings before they can be used with another Apple Account. Please note that devices locked with a passcode are protected by passcode encryption, and Apple can’t help remove the passcode lock without erasing the device.

Apple does indeed require legal documentation before they can assist in a deceased person's Apple Account, which usually is a court order that names you the rightful inheritor of their data.

Once you have obtained that, you can submit a claim to Apple here:

How to request access to a deceased family member’s Apple Account - Apple Support