Uh, pilots do not know everything.
Technical expertise might be worthwhile.
A smart lawyer might ensure thoroughness, such as checking for CO in blood of dead persons - AU’s investigators failed to do that in one case, a doctor questioned their report, fortunately tissues were still available to analyze, CO in blood of pilot and front seat passengers. Cause was exhaust from a crack leaking through a botched reinstallation of an access panel in firewall.
As far as determining ‘probable cause’, be aware that investigations take thorough work to ensure things aren’t overlooked, that can take months or more.