Since I mentioned about "Second Space", let's take a look at Samsung "Secure Folder". This built-in feature for Samsung smartphones is a secret space for storing images, videos, documents and apps. And most important of it, it's encrypted.
All you have to do is sign in with your Samsung cloud account and create a secure folder. You could decide the authenication method such as PIN, Password or Pattern Lock.
Suspects may make copies of Apps such as WhatsApp, WeChat, LINE...in "Secure Folder" for communicatoin with his/her parterns in crime. No ones knows what's inside the "Secure Folder". Even mobile forensic tools could extract all files from a Samsung smartphone, guess what? Those data in "Secure Folder" is meaningless because all data is encrypted. Only you could know is filename and its path, but you will never know its content.
It sounds like there is nothing you could do about decrypting Samsung "Secure Folder". Fortunately you could try to access the suspect's Samsung Cloud and you still got a chance to find backup data in "Secure Folder".