As Apple describes in their PRO tips about Mac OS, there’s an option to empty your trash securely. Does this option affect Disk Drill and its file recovery technology? Yes, it does.
The main idea behind emptying trash securely is not just marking the space occupied by erased files as empty, but also overwriting this space with garbage (usually just zeros). This is a security feature and it is intended to make your deleted files unrecoverable.
The main idea behind data recovery techniques like Disk Drill’s “Deep Scan” is reading the data in a binary format directly from the space marked as empty on your hard drive and then rebuilding the file structure. Unfortunately once this space is overwritten with zeros, your original files are gone for good, as there’s no multi-layer data storage yet invented.
So, yes, secure trash emptying will probably make the files in the trash unrecoverable for good. While this is surely a great way to remove the files you don’t want anyone to see, this also doesn’t let Recovery Vault or Deep Scan recover your files later on. So, if you are concerned about unexpected data loss in future, we recommend disabling this feature in your Finder Preferences, and not using the option to empty trash securely from the main menu.