Jennifer Hudson batted 1.000 with the jurors on the William Balfour murder case … because every single one of them admitted they knew who she was BEFORE the trial began.

TMZ obtained the juror questionnaires — filled out by all of the prospective jurors before they were empanelled on the jury to determine the fate of the man accused of murdering Hudson’s family.

Of the final 12 — 5 of the jurors admitted they had seen Hudson in “Dreamgirls” … and 6 said they recognized Jennifer from her days on “American Idol.”

The lone juror who didn’t see Jen’s Oscar winning performance or “Idol” said he knew Hudson from television … but didn’t specify which show he recognized her from.

One legal expert tells us … Hudson’s level of celebrity probably didn’t hurt the case against Balfour … because jurors tend to identify with famous people.

It also didn’t hurt that Balfour couldn’t have been more guilty.

As we previously reported, he was convicted for murdering Jennifer’s mother, brother and nephew and is due to be sentenced very soon.