Can police access the backup photos after seizing my iPhone?

police seized my phone bcs someone thats my age sent some pics and they want them took down. i was called there as a witness but i don’t understand why they took my phone because i told them i dont have the pics (they sent me the pics but i didn't save em cuz they weren’t allat) they took my phone with my sim card and i told them what should i do if i have no phone, they said that i should buy a new one or get a older one. i deleted the backup after they took my phone and put it in airplane mode do they have access to my backups or they were deleted?

[Re-Titled by Moderator]