[SPOILER] A Marriage Made in Heaven

[bakagaijin]

Does anyone know how to gather enough evidence to arrest both Leroy and Lorna?

[ShadowAngel]

That's not possible.
There are only 2 endings depending on when you find the Knife:

If you find the knife on your first visit to the crimescene it will always end with Leroy killing Lorna.

If you find the knife on a later visit back to the crime scene it will end with your chasing Leroy, either you stop him with a warning shot or you have to kill him later as he takes a hostage (or you just shot him while he runs) and that's it. They don't really say what happens to Lorna but i'm pretty sure she just gets arrested by some other cop and put into jail.

[bakagaijin]

Then why do the end notes say If I gathered more evidence I could have arrested Lorna too?