As part of the statutory mandate of "substantial justice," however, Arizona courts have carefully guarded a party's right to cross-examine the author of any document that the Administrative Law Judge considers as substantive evidence. See Schnatzmeyer v. Industrial Comm'n, 78 Ariz. 112, 114, 276 P.2d 534, 535 (1954) (an opponent has a right to cross-examination "by decision of this court if the commission is to use as evidence reports of investigators and doctors or ex parte affidavits"); Obersteiner v. Industrial Comm'n, 161 Ariz. 547, 549, 779 P.2d 1286, 1288 (App. 1989) ("The right to cross-examination is fundamental and attaches when the Industrial Commission receives any testamentary or documentary evidence."); Division of Fin. v. Industrial Comm'n, 159 Ariz. 553, 556, 769 P.2d 461, 464 (App. 1989) ("The right of cross-examination is necessary for substantial justice."); Jones v. Industrial Comm'n, 1 Ariz. App. 218, 222, 401 P.2d 172, 176 (App. 1965) ("where the Commission uses evidence, testimony, reports, documents, affidavits or any matter which may appear in the file upon which to base an award, there must be full and complete opportunity on the part of the parties to cross-examine"); see also 7 Arthur Larson & Lex K. Larson, Larson's Workers' Compensation Law 127.11[3][a]-[b], at 127-47 (2000) (characterizing the right of cross-examination as rule of evidence protecting elementary fair play). There are some exceptions. "As a general rule, an administrative law judge may deny a timely subpoena request if the expected testimony would not be material or otherwise necessary." Hughes v. Industrial Comm'n, 188 Ariz. 150, 152, 933 P.2d 1218, 1220 (App. 1996). The right may also be waived. See Davis v. Industrial Comm'n, 103 Ariz. 114, 116-119, 437 P.2d 647, 649-52 (1968) (party must specifically identify witness desired for cross-examination or the right is waived). Other states addressing this issue have given the administrative judge discretion to admit the report of a deceased doctor under appropriate circumstances. See, e.g., Hercules, Inc. v. Walters, 434 So. 2d 723, 725-27 (Miss. 1983); Cascio v. Standard Oil Co. of N.J., 32 So. 2d 66, 68 (La. Ct. App. 1947); Cristofaro v. State Accident Ins. Fund, 19 Ore. App. 272, 527 P.2d 412, 413-14 (Or. Ct. App. 1974). for example, in Hercules, the administrative judge admitted a medical report although the authoring doctor had died and was not available for cross-examination. The Supreme Court of Mississippi held that the report would be admissible in court under the rules of evidence and that admission was therefore consistent with the non-technical standards for administrative proceedings. See Hercules, 434 So. 2d at 727 ("We hold that the report of Dr. Ross was competent evidence as an exception to the hearsay rule."); see also Cascio, 32 So. 2d at 68 (report of deceased doctor admissible in commission proceedings under the business records exception to hearsay rule); Cristofaro, 527 P.2d at 413 (affirming admission of deceased doctor's report under a statute requiring that Commission proceedings be conducted to achieve "substantial justice").