Sources close to Daniel tell TMZ ... Silva had been working hard all day leading up to the deadly crash, and showed up to Corey's birthday party totally sober. We're also told Daniel was only at the party for 2 hours, but was seen drinking White Claw hard seltzer.

We broke the story ... Daniel was arrested and charged with 2nd-degree murder after wrecking a black McLaren sports car earlier this month. Corey, his passenger in the car, died from injuries suffered in the crash. They had just left Corey's 25th birthday party.

Daniel's attorney, Mike Cavalluzzi, tells TMZ ... "This is a horrible tragedy and our hearts go out to Corey's family and friends. We are reviewing all of the evidence and will reserve comment for a later time. For now, it is most important that everyone involved is given time and space to grieve."

Remember ... our law enforcement sources say witnesses claim Silva allegedly tried to flee the scene but was stopped by bystanders. Witnesses also say Daniel was drinking before getting in the driver's seat, but he has NOT been charged with DUI.

We're told Cavalluzzi believes prosecutors will not be able to prove beyond a reasonable doubt Daniel was driving drunk. He says the crash was nothing more than a horrible accident.