mobile

My mother's phone has an audio recording that needs to be recovered before a court date, but the digitizer is broken and the screen is locked. ROM is stock, recovery is stock, bootloader is locked, usb debugging is disabled. I know how to crack passwords / pins on android with a variety of methods, but most require an adb shell or an exploit on an older android version. The few that don't happen through update.zip or the JTAG interface. I can access fastboot and adb sideload. So, I'm thinking maybe I can apply an OTA update that disables the screen lock and/or enables USB debugging. However, since the recovery is stock, the zip package needs to be signed and my attempts keep giving "footer is wrong" or "whole file verification error". It seems to be running Android 5.0.1 because that OTA update will work (but I cannot modify it). The CWM update.zip will not work either (because of verification issues). What are my options here?