Even truecrypt is not a promise of freedom. The more money they want to spend, the deeper they can go. Even hdd that have been physically destroyed in fires and salt water have been recovered enough.
Best thing to do is to not view it.
Second best is to only browse on system you have made it impossible to download from. Cellphones are easy to do this with in the settings. Make sure the system is expendable. If you ever did get a hunch that LEA is looking at you, you can destroy and throw away the system.
Downloading or saving any images or videos, reguardless of how grey area they are, is a bad idea. Forensics analysts rely on people like us being hoarders and saving things. The first things they search for in an investigations image are deleted files, browser history, and emails.
Browser history is in possession of the person whos using it. Just delete it after each use along with all data stored for the program your using.
Again, the best way to not get bit is not to play with the snake. If your confidant enough to bring the snake home and put it in a drawer to play with whenever you want then you can expect to eventually get bitten.
Thats why a lot of imageboards and hidden sites will post photos, gifs, and webms. That way, you dont have to download the files. Remember, a deleted file is never truly gone. You can delete a video, wile your hard-drive in a secure wipe, install a different OS, and the video can still be recovered and played in full. If you have NN images on your PC now, I would suggest gettijg a new PC and preparing to destroy and hide the first one. I would go as far as throwing the pieces away in a different city.
Pornagraphy is define as ANY image, media, drawing, or audio that is intended to draw on or implement sexual thoughts or desires. Having a cartoon of a loli in a bakini is not doing you favors in a courtroom. Unless you are a photographer who does sessions for local sports teams, why would you have photos of underaged girls in bakinis and leotards. The DA will be very nasty with you and it wont be a challenge to turn the foom against you. The less you give them to work with, the better.