In People v. Zehr, 103 Ill. 2d 472, 477, 469 N.E.2d 1062, 83 Ill. Dec. 128 (1984), our supreme court held that a trial court erred during voir dire, when it refused the defense counsel's request to ask potential jurors about four fundamental principles of law. Zehr, 103 Ill. 2d at 476-78. In Zehr, our supreme court held that it is "essential to the qualification of jurors in a criminal case ... that they know" these four fundamental principles: (1) that defendant is presumed innocent; (2) that defendant was not required to produce any evidence on his own; (3) that defendant must be proved guilty beyond a reasonable doubt; (4) that defendant's failure to testify on his own behalf could not be held against him." Zehr, 103 Ill. 2d at 477. These four principles are now commonly known as the "Zehr principles." See: People v. Jocko, 389 Ill. App. 3d 247, 259, 906 N.E.2d 38, 329 Ill. Dec. 193 (2009); People v. Martinez, 386 Ill. Ap. 3d 153, 158, 897 N.E.2d 879, 325 Ill. Dec. 340 (2008); People v. Gilbert, 379 Ill. App. 3d 106, 109, 882 N.E.2d 1140, 318 Ill. Dec. 17 (2008); People v. Yarbor, 383 Ill. App. 3d 676, 681, 889 N.E.2d 1225, 321 Ill. Dec. 665 (2008).