There are no rules of evidence on television but that is where most folks learn to practice law.
On television lawyers can do anything, present anything and say anything and the judge always follows the script. The problem of evidence in real courtrooms is that this is not television and what may be admissible in fiction may not be admissible in a real court.
If you think about it Rules of Evidence are important so the fate of people and their property are not just a question of emotion or prejudice or the right scriptwriter, and instead their fate is based on what is reliable, or authentic, or can withstand a good questioning.
People come to me with their opinions and declare it to be evidence. Bits of paper that may support their position become facts set in stone when handled by them, but go up like so much smoke when marked by the clerk, offered as evidence then objected to on any number of basis; hearsay, authentication, the best evidence rule, the list goes on.
Then they get mad. Well fine, be mad, but what you see on TV is not evidence.