Anyone who has ever used an iPhone knows that there is a feature on the iPhone that has a "recently deleted" folder in your album, which is dedicated to recovering deleted photos.But if I don't want to recover these photos, how can I delete them altogether? I don't want anyone else to get them.
Law enforcement / specialist data recovery companies have the capability to potentially recover deleted files from phones using commercially available software. With any data storage device the data is only truly deleted when it is successfully overwritten
If you are paranoid that someone is going to steal your phone, break the virtually unbreakable encryption just to recover your deleted pictures then either upload music or videos or whatever from iTunes that completely fills the phone then delete it.