That once in the lifetime experience - it is symbolized with caps and gowns,
Use a dash and lowercase "it".
more rigorous courses
Course should be plural.
Other than being valedictorian, participating in a summer internship at Derrick Strahorn Law Firm is another one of my short-term goals.
Eliminate the commas.
defendant sends goose bumps through my body.
Eliminate the comma.
Now my next step is changing this thought to aid my long-term goals.
This sentence doesn't fit or work.
I believe that the more I know about a specific crime and the criminal's intention, the better I can prosecute that criminal in court. It will be just like a sudoku puzzle.
I made "criminal" posessive and I rephrased some of your sentence. I don't think law is anything like a sodoku puzzle, so eliminate that sentence. If you want, you can make a new ending sentence, but you don't have to.
Aside from those errors, your grammar is fine. You've done a much better job in answering the prompt this time than the first.
Good luck!