UNITED STATES COURT OF APPEALS
FOR THE TENTH CIRCUIT

________________ _________________ KEENAN, HOPKINS, SUDER, AND STOWELL CONTRACTORS, INC., d/b/a KHS&S Contractors, Petitioner,

v. DEPARTMENT OF LABOR, Respondent. No. 20-9537 (OSHC No. 18-1306)

________________ _________________ ORDER AND JUDGMENT *

________________ _________________ Before TYMKOVICH , Chief Judge, BALDOCK and EID , Circuit Judges.

________________ _________________ Keenan, Hopkins, Suder, and Stowell C ontractors, Inc. (KHS&S) petitions for review of a final decision by the Occ upational Safety and Health Review Commission (Commission) finding that KHS&S had committed a serious violation of an applicable safety and health standa rd. Exercising jurisdiction pursuant to

* After examining the briefs and appella te record, this pa nel has determined unanimously that oral argument would not ma terially assist in the determination of this appeal. See Fed. R. App. P. 34(a)(2); 10th Cir. R. 34.1(G). The case is therefore ordered submitted without oral argument. This order and judgment is not binding precedent, except under the doctr ines of law of the case, res judicata, and collateral estoppel. It may be cite d, however, for its persuasi ve value consistent with Fed. R. App. P. 32.1 and 10th Cir. R. 32.1. FILED United States Court of Appeals Tenth Circuit 

### April 15, 2021 Christopher M. Wolpert Clerk of Court2 29 U.S.C. § 660(a), we de ny the petition for review and affirm the Commission’s decision. I. Procedural Background While investigating an unrelated acciden t at a job site in Littleton, Colorado, an Occupational Safety and Health Administ ration (OSHA) investigator learned that KHS&S employees were climbing on, standi ng on, and working from the guardrails of an aerial lift basket to perform their work. Upon the investigator’s recommendation, the Secretary issued KHS&S a citation for a serious violation of 29 C.F.R. § 1926.453(b)(2)(iv), which requires that “[e]mp loyees shall always stand firmly on the floor of the bask et [of an aerial lift], and shall not sit or climb on the edge of the basket or use planks, ladders, or other devices for a work position.” The citation proposed a penalty of $5,543. KHS&S contested the citation with the Secretary of Labor, triggering review by the Commission. See 29 C.F.R. § 659(c). An ad ministrative law judge (ALJ) presided over a one-day trial, after whic h both parties submitted post-trial briefs. The ALJ issued a written decision on Janua ry 17, 2020, affirming the citation and assessing a penalty of $5,543. When th e Commission declined discretionary review, the ALJ’s decision became a final order of the Commission on February 20, 2020. See F & H Coatings, LLC v. Acosta , 900 F.3d 1214, 1220 (10th Cir. 2018).
II. Discussion In its petition for review, KHS&S cont ends that the ALJ erred: (1) by not allowing KHS&S sufficient time to prepare it s defense after disc losure of witness3 statements; (2) in finding that KHS&S knew or should have known that its employees were working from the railings of the aerial lift basket; and (3) in finding there was a serious violation of § 1926.453(b)(2)(iv).
A. Time to Review Witness Statements 1. Relevant Background It was undisputed that two KHS&S employees, Fernando Ruiz Moya and Martin Rojas, had stood on the guardrails of an aerial lift bask et while installing drywall on the exterior upper levels of a building that was under construction. During the investigation, Ruiz Moya and Rojas each provided a statement. The Secretary withheld their st atements during discovery pursuant to the government informer’s privilege. The Secretary then listed Ruiz Moya and Rojas as fact witnesses in a pretrial st atement, which was served on KHS&S a week before the trial. At the beginning of the trial, KHS&S inquired whether there were witness statements from Ruiz Moya and Rojas. Co unsel asked to view any statements and sought a “short recess in order to re view them and prepare before [cross examination].” Trial Tr. at 21. The AL J construed counsel’s request as seeking production of prior statements at that time. Following the Commission’s caselaw, however, the ALJ ruled that th e Secretary would be require d to produce an informer witness’s prior statement only after the witness’s direct ex amination, at which point4 the ALJ would recess to allow KHS&S tim e to review the statement before proceeding with cross examination. After Ruiz Moya’s direct examination, the Secretary produced his statement. Following a twenty-minute rece ss, the trial resumed with the ALJ stating: “I know you had a pretty short amount of time to review what you said was a 65-page interview statement with the witness. Are you ready to proceed with your cross-examination?” Id. at 63. KHS&S’s counsel responded: I would, your Honor, like to make anobjection, just for the record, though, about the w itness statement.

. . . . . . First, we would like to objectthat the Secretary did not produce redacted copies of the st atements during discovery. Secondly, we believe under . . . a Tenth Circuit case, that these statements should have been produced at the tim e the Secretary identified the witnesses on the pretrial statement. Alternatively, we believe they shou ld have been produced at the start of the hearing today, once the Secretar y knew that she was, in fact, calling the witness since it was, in fact . . . I think it’s about 75 pages of a transcript. So we believe that the Responden t has been prejudiced by the fact that they have been produced after th e witness has testifie d with only about 20 minutes to review the transcript. Id. at 63-64. Counsel did not request additi onal time to review Ruiz Moya’s witness statement. The ALJ overruled KHS&S’s ob jections and counsel proceeded with the cross examination. Rojas was the next witne ss called after Ruiz Moya. Before he testified, KHS&S renewed its request for his prior stat ement. Over the S ecretary’s objection,5 the ALJ ordered the Secretary to produce Rojas’s statement before his direct examination because it was clear he was going to testify. Rojas’s statement was approximately the same length as Ruiz Moya ’s statement. The ALJ recessed for a one-hour lunch break during Rojas’s direct testimony. When his direct testimony concluded, KHS&S’s counsel proceeded w ith cross examination without making any objection or asking for additional time to review Rojas’s prior statement. In its post-hearing brief, KHS&S ar gued that the ALJ had misapplied the government informer’s privilege and had provided insufficient time to review the informer witnesses’ statemen ts such that KHS&S could not adequately prepare for cross examination. 2. The Government Informer’s Privilege “The government is privileged to w ithhold from disclosure the identities of persons furnishing information of law violations to law enforcement officers. The purpose of the privilege is the furtherance and protection of the public interest in effective law enforcement.” Usery v. Loc. Union 720, La borers’ Int’l Union of N. Am., AFL-CIO , 547 F.2d 525, 527 (10th Cir. 1977) (citation and internal quotation marks omitted). “The principle applies in both civil and criminal actions.” Id. This court has applied the government informer’s privilege, for exam ple, in actions under the Fair Labor Standards Act. See id. The Commission has also long held that the privilege applies in pr oceedings before it. See Massman-Johnson (Luling) , 1980 CCH OHSD ¶ 24436, 1980 WL 1059 3, at *3 (No. 76-1484, 1980). “The informer’s privilege belongs to the government . . . .” Id. at *10. And “the mere fact6 that [an employee] supplied information re levant to the investigation of alleged OSHA violations makes the privilege applicable.” Id. at *4. The Commission has stated th at “[t]he essence of the informer’s privilege . . . is the protection of the info rmer’s identity, and the c onfidential information in a statement is that which tends to indicate that the person giving it has cooperated with the government against the employer.” Id. Thus, witness stat ements are protected from disclosure because “the identity of an informer mi ght be revealed from the disclosure of even a basical ly factual statement relevant to an investigation, for example, if the tone and manner of the st atement were accusatory or unfriendly to the respondent.” Id. The “concern [is] over possibl e witness harassment due to premature disclosure of witness statements ,” such as “pressure by the employer . . . involved on the employees or others to change their testimony or discourage them from testifying.” Id. at *7.
In Massman-Johnson , see id. , the Commission discussed a case in which the Eighth Circuit held that the a ppropriate time for disclosure of informer statements is left to the trial court’ s “sensitive discretion,” Brennan v. Eng’red Prods., Inc. , 506 F.2d 299, 304 (8th Cir. 1974). Brennan had set forth several options for the timing of disclosure, including the approach applied in federal criminal cases under the Jencks Act, pursuant to which a defe ndant is allowed to examine a government witness’s prior statement onl y after the witness has comp leted testifying on direct examination. See 506 F.2d at 304-05; 18 U.S.C. § 3500(b). Ultimately, the Commission decided to adopt the Jencks Ac t approach in proceedings before it,7 see 1980 WL 10593, at *9, unless, how ever, the respondent has made a “particularized showing of need for any of the statements them selves before the hearing sufficient to outweigh the str ong public interest in protecting the confidentiality of government sources,” id. at *11. Also consistent wi th the Jencks Act, see 18 U.S.C. § 3500(c), the Commission set forth a procedure to allow for review of an informer witness’ s statement that is disclosed after dire ct examination: The Respondent shall be entitled to a recess for such reasonable time as is necessary to evaluate a stat ement and prepare to use it in the hearing. In the event that a statement disclosed at th e hearing contains material that the respondent could not have discovered previously and that bears on the issues in the case, the respondent sh all be entitled upon request to a recess or continuance for such time as is re asonably necessary to meet or take advantage of th e new evidence. Massman-Johnson , 1980 WL 10593, at *9. It furt her stated that “any unfair surprise may be cured by a recess or continuance.” Id. at *10.
3. Standard of Review We apply the same standard of revi ew to the ALJ’s decision as we would apply to an order actually issued by the Commission. See F & H Coatings , 900 F.3d at 1221. KHS&S argues the time allotted by the ALJ for its review of the prior statements by Ruiz Moya and Rojas after they were produced by the Secretary was unreasonable. But it does not clearly articulate what sta ndard of review this court should apply. It contends the ALJ’s decisi ons were “not in accordance with the law,” Pet. Opening Br. at 15, but it fails to explain how a reasonabl eness determination raises a legal question. KHS&S also argue s that the ALJ abused his discretion.8 See id. at 2, 28. For several reasons, we c onclude that the determination of what amounts to a reasonable amount of time in this context is a matter within the discretion of the ALJ. First, the Commission modeled its rule fo r the timing of disclosure of informer witness statements on the Jencks Act. See Massman-Johnson , 1980 WL 10593, at *9. Under the Jencks Act, th e amount of time permitted for a criminal defendant to review a government witness’s statement is subject to the court’s discretion.
See § 3500(c); see also Ogden v. United States , 303 F.2d 724, 738 n.51 (9th Cir. 1962) (“The recess which the Court in the exercise of its discretion (18 U.S.C.A. § 3500(c)) granted to defendant to examine the statement was shor t, but in all the circumstances we cannot say that it was so unreasonably short as to constitute an abuse of discretion.”). Moreover, outside of the crimin al context, this court has applied an abuse-of-discreti on standard in reviewing dist rict courts’ application of the government informer’s privilege. See Usery , 547 F.2d at 528; Brock v. Gingerbread House, Inc. , 907 F.2d 115, 117 (10th Cir. 1989). Finally, we also review issues related to the grant or de nial of a continuance for an abuse of discretion. See Morrison Knudsen Corp. v. Fireman’s Fund Ins. Co. , 175 F.3d 1221, 1229 n.4 (10th Cir. 1999) (re viewing a district court’s denial of a continuance); Robinson v. United States , 718 F.2d 336, 338 n.1 (10t h Cir. 1983) (reviewing an ALJ’s denial of a continuance). We will therefore review for an abuse of discretion the ALJ’s determinations in this case regarding the time allotte d KHS&S to review informer witness9 statements. And we “will find error only if the decision was arbi trary, capricious, whimsical or manifestly unreasonable, or we are convinced that the tribunal made a clear error of judgment or exceeded the bounds of permissible choice in the circumstances.” F & H Coatings , 900 F.3d at 1223 (brackets and internal quotation marks omitted).
4. KHS&S’s Contentions Under Massman-Johnson , KHS&S was “entitled to a recess for such reasonable time as is necessary to evaluate a statement a nd prepare to use it in the hearing.” 1980 WL 10593, at *9. KHS&S first contends that the time permitted by the ALJ—twenty minutes to review Ruiz Moya’s sevent y-five page statement and one hour to review Rojas’s sixty-five page statement—was insufficient under Massman-Johnson . But the Commission did not deci de in that case how much time is reasonable under particularcircumstances. Here, KHS &S tells us nothing about the circumstances beyond the length of the w itnesses’ statements and the duration of the recesses. It does not point to where the statemen ts are contained in the administrative record, nor have we f ound them. And despite KHS&S’s assertion otherwise, it is not obvious ba sed solely upon a stated number of pages that the time allotted by the ALJ for review was manifestly unreasonable. For example, one court held it was an abuse of discretion to deny a defendant’s request for additional time to review Jencks Act material that ha d been produced one day before the trial began, which consiste d of one thousand pages of testimony (an eight-inch stack of paper) and a forty-five minute video tape. See United States v.10 Holmes , 722 F.2d 37, 40-41 (4th Cir. 1983). But another court held there was no abuse of discretion in allowing only nine minutes to review a stack of papers one-quarter the size of that produced in Holmes

. See United States v. Stanfield , 360 F.3d 1346, 1356-58 (D.C. Cir. 2004). Th e volume of paper in this case appears to be comparable to that produced in Stanfield , in which the court concluded that “[n]o one would accuse the dist rict court here of being ov erly generous in affording counsel time to review the documents pr oduced after [the gove rnment witness’s] testimony; indeed, the court flirted with th e outer limits of its discretion, but we cannot conclude that it a bused that discretion.” Id. at 1358. Nor does KHS&S cite any case in which a comparable recess to review a sim ilar volume of material was held to constitute an abuse of discre tion. We conclude that KHS&S has not demonstrated an abuse of discretion by th e ALJ based solely upon the length of the witnesses’ statements and the duration of the recesses after they were produced. KHS&S also appears to contend that the ALJ abused his discretion by not granting an additional reces s or a continuance. See Pet. Opening Br. at 19 (“The ALJ decided that a short break and then a lunc h break would suffice instead of granting a recess or a continuance of the hearing.”) . But KHS&S never sought an additional recess or a continuance of the trial. When asked by the ALJ if she was ready to proceed with Ruiz Moya’s cross examin ation, KHS&S’s counsel made objections “just for the record” regard ing the Secretary’s failure to produce the witnesses’ statements either before tria l or at the beginning of tria l. Trial Tr. at 63. She concluded by asserting (withoutelaboration) that KHS&S had been prejudiced by the11 production of Ruiz Moya’s statement after he testified “with onl y about 20 minutes to review the transcript.” Id. at 64. When the ALJ overru led these objections, counsel proceeded to cross examine Ruiz Moya. Then, after the lunch break and the conclusion of Rojas’s direct examination, counsel proceeded wi th cross examination without offering any objection, much less a request for additional time to review Rojas’s prior statement. See id. at 109. We will not fault the ALJ fo r failing to grant a furthe r recess or a continuance when no such request was made. In particular, under Massman-Johnson , if a witness’s “statement disclose d at the hearing contains ma terial that the respondent could not have discovered previously . . . the respondent shall be entitled upon request to a recess or continuance for such time as is reasona bly necessary to meet or take advantage of the new evidence.” 1980 WL 10593, at *9 (emphasis added). Although this is precisely th e type of prejudice that KHS&S contends it suffered, it made no such request during the trial. KHS&S asserts that it fi rst learned at trial thatthe Secretary alleged a particular supervisor, Ricardo Cereceres, had authorized employees to work from the guard rails of the aerial basket or knew that they were doing so. KHS&S claims that “[w]ithout time to prepare with Mr. Rojas’ pr ior statement, [it] had no way to test the12 veracity of his multiple statements made at trial.” Pet. Opening Br. at 11. 1 It contends this “amounted to trial by ambush.” Id. at 19. There are several problems with thes e contentions. First, KHS&S argues it was prejudiced because it was unaware of uns pecified “material” in the witnesses’ prior statements due to the Secretary’s fail ure to disclose them before the trial. Id. at 18. But it fails to demonstr ate that the ALJ abused hi s discretion by ordering their disclosure after (or just before) the witnesses’ direct examinations. 2 KHS&S also does not show how its alleged prejudice relate s to new information in the witnesses’ prior statements, which, as we have noted, are absent from the ad ministrative record. But even assuming that either or both of the statements alleged knowledge or authorization by Cereceres, KHS&S igno res the Commission’s holding that, when

1 It appears that KHS&S focuses on Rojas’s prior statement and testimony because Ruiz Moya did not testify that Cereceres authorized him to stand on the railing of the aerial basket.

2 KHS&S challenges the timing of disc losure of the informer witness statements in a perfunctory manner in a footnote of its opening brief. See Pet. Opening Br. at 18 n.2. It argues the Secretary was obl iged to produce redacted statements before the trial if their contents did not reveal the informers’ identities. But it fails to demonstrate th is was the case. And the Commission has noted that “a rule requiring pretrial disclosu re of witness statements ge nerally, even with deletions, may result in unnecessary disclo sure of informers’ identities ” and also “might lead to extensive in camera proceedings and place an unwarranted administrative burden upon judges.” Massman-Johnson , 1980 WL 10593, at *10. KHS&S also argues the Secretary could have produced the prior st atements when Ruiz Moya and Rojas were listed as witnesses in the S ecretary’s pretrial statement. But the Commission has held “that submission of a witn ess list . . . does not c onstitute a waiver of the confidentiality of the identities of in formers or their statements.” Id. at *5. Ultimately, KHS&S fails to show that th e ALJ abused his discretion by timing the Secretary’s disclosure of the informer w itnesses’ statements consistent with the Commission’s holding in Massman-Johnson

.13 “the problem of surprise at trial due to th e contents of a witnes s statement” arises, “any unfair surprise may be cure d by a recess or continuance,” Massman-Johnson 1980 WL 10593, at *10. A nd despite having an hour to review Rojas’s statement and hearing his direct testimony regarding Cereceres’s author ization, KHS&S did not ask the ALJ for additional time either to prepar e for the cross examin ation or to offer other rebuttal evidence. KHS &S therefore fails to dem onstrate it was prejudiced by having insufficient time to prepare its defense after the Secretary produced the witnesses’ statements. See United States v. Arboleda , 929 F.2d 858, 864 (1st Cir. 1991) (treating “with skepticism . . . cl aims of prejudice when accompanied by a failure to attempt at trial to mitigate the perceived harm”). We reject KHS&S’s first claim of erro r because it has not id entified an abuse of discretion by the ALJ in the timing of the Secretary’ s disclosure of informer witness statements or in the amount of time allotted for review of such statements. It also failed to make any attempt to cure or mitigate any prejudice. We ultimately cannot say that the ALJ’s decisions were arbitrary, capricious, whimsical or manifestly unreasonable, nor are we convinced that the ALJ made a clear error of judgment or exceeded the bounds of perm issible choice in th e circumstances. B. ALJ’s Finding That KHS&S Knew or Should Have Known of the Violation Section 1926.453(b)(2)(iv) requires th at “[e]mployees sh all always stand firmly on the floor of the bask et [of an aerial lift], and shall not sit or climb on the edge of the basket or use planks, ladders, or other devices for a work position.” To14 establish a violation of an OSHA safety and health st andard, the Secretary must demonstrate the following elements by a pr eponderance of the evidence: “(1) the applicability of the standard , (2) the employer’s noncomplia nce with the terms of the standard, (3) employee access to the viol ative condition, and (4) the employer’s actual or constructive knowled ge of the violation.” Jake’s Fireworks Inc. v. Acosta , 893 F.3d 1248, 1256 (10th Ci r. 2018). KHS&S challenges the ALJ’s finding on the fourth element: that it knew, or with re asonable diligence should have known, that its employees were working from the aerial basket railings.
1. Standard of Review We will uphold an ALJ’s factual findi ng if it is supported by substantial evidence. See F & H Coatings , 900 F.3d at 1221; 29 U.S.C. § 660(a). Substantial evidence is such relevant evidence as a reasonable mind might accept as adequate to support a conclusion, and it must be enough to justify, if the trial were to a jury, a refusal to direct a verdict when the conclusion sought to be drawn from it is one of fact for the jury. F & H Coatings , 900 F.3d at 1221 (internal quotati on marks omitted). “[W]e do not reweigh the evidence, second-guess the f actual inferences drawn therefrom, or substitute our judgment on the credibility of witnesses.” Id. (internal quotation marks omitted). 2. Relevant Background Ruiz Moya and Rojas were using an aerial lift to instal l sheets of drywall— which measured four feet by eight feet and weighed forty pou nds—on the exterior upper levels of a building approximately sixty to eight y feet above the ground.15 Because of certain as pects of the building under cons truction, the distance from the aerial lift basket to the point of installa tion was sometimes three to four feet. Cereceres and another superv isor, Morgan Payne, directed Ruiz Moya and Rojas to install self-retracting lanya rds, also called “yo-yos,” on the building’s steel I-beams above the basket so that they could tie-off when stepping out of the basket. The ALJ found that Ruiz Moya and Rojas consistently testifie d that, when installing the drywall sheets, they sometimes stood with one or both feet on the aerial basket railing. They also sometimes used the basket railing to climb out of the basket when it was not possible to open the gate due to the position of the basket relative to the building. The ALJ also pointed to testim ony that Payne and Cereceres authorized the employees to stand on the basket railing to get their job done, as long as they tied-off to a yo-yo. The ALJ found that KHS&S either knew, or with the exercise of reasonable diligence should have known, that Ruiz Moya and Rojas were repeatedly standing on, climbing on, and working from the aerial li ft basket railings. The ALJ found the evidence showed that these employees were doing so multiple times per hour throughout the day. Finding that the aerial lift was visible from the main entrance to the job site as well as fro m KHS&S’s job trailer, the ALJ concluded that “the violative condition was open, obvious, and in pl ain view.” ALJ’s Dec. & Ord. at 9. The ALJ also pointed to the following evidence regarding the supervisors’ knowledge:16 Supervisors Payne and Cereceres ackn owledged providing [the employees] with a yo-yo strap to enab le them to climb out of the basket as needed. Payne, and to a lesser extent Cerecere s, were seen walking around the job underneath the two employees throughout the day. Payne even repaired their stuck aerial lift twice. Ce receres stopped and commented on the location of their yo-yo on one occasion. Id. The ALJ found that, “[w]ith the exercise of reasonable diligence, both Payne and Cereceres should have known what Ruiz [Moya] and Rojas were doing to perform their assigned task.” Id.
3. KHS&S’s Contentions KHS&S argues the ALJ’s knowledge findi ng is not supported by substantial evidence. But its contentions ask this court to ignore substantial evidence in the record, reweigh the evidence, draw different inferences than th e ALJ, or reassess witness credibility. KHS&S argues the ALJ “fail[ ed] to rectify the incons istences in Mr. Rojas’ testimony at trial” regarding who authorized him to work from the aerial lift basket railings. Pet. Opening Br. at 21. But th e ALJ pointed to Rojas’s testimony that he received authorization from both Cerecer es and Payne. And KHS&S does not explain why a reasonable jury coul d not rely on that evidence. See F & H Coatings , 900 F.3d at 1221. It also contends there was inconsiste nt or conflicting testimony regarding how often the employees were working from the railings, as well as the distance and visibility from the job tra iler to the aerial lift. KHS&S argues the “facts show that the condition did not exist long enough to es tablish [it] failed to use reasonable17 diligence to gain knowledge.” Id. at 25. Again, however, this contention fails to demonstrate that the eviden ce actually relied on by th e ALJ was insubstantial. KHS&S argues the evidence that Payne and Cereceres were attentive to the employees working in the aerial lift ba sket shows their r easonable diligence in enforcing safety standards rath er than their knowledge of vi olations. It also contends the evidence that KHS&S implemented work rules, trained empl oyees, inspected the job site, and supervised and disciplined employees shows it was unlikely that KHS&S management would permit employees to stand on the railings to do their work. But these assertions merely ask us to draw diffe rent inferences from the evidence than the ALJ. Finally, KHS&S argues the ALJ shoul d have relied on the testimony of Christian Mancera, its Regional Safety Engi neer, regarding its l ack of knowledge. But it ignores that the ALJ “did not find Mr. Mancera to be very credible.” ALJ Dec. & Ord. at 11 n.3. And we defer to the ALJ’s cr edibility determinations. 3
KHS&S fails to demonstrate that the ALJ’s finding as to its knowledge of the violation was not supported by substantial evidence.

3 In addition, KHS&S appears to conced e that the testimony of Ruiz Moya and Rojas constitutes substantia l evidence supporting the ALJ’s knowledge finding. See Pet. Opening Br. at 19; Reply Br. at 8-9.18 C. ALJ’s Finding That KHS&S’s Violation Was Serious Violations of OSHA safety and health standards are classified based on their seriousness. See Jake’s Fireworks , 893 F.3d at 1256 (noting vi olations can range from “de minimis” to “willful”). [A] serious violation shall be deemed to exist in a place of employment if there is a substantial probability that death or serious physical harm could result from a condition which exists, or from one or more practices, means, methods, operations, or processes which have been adopted or are in use, in such place of employment. 29 U.S.C. § 666(k). The Secretary need not prove a substantial probability that an accident would occur; rather he need only s how that if an accide nt were to occur, death or serious physical harm could result. See Kent Nowlin Constr. Co. v. Occupational Safety & Health Rev. Comm’n , 648 F.2d 1278, 1282 (10th Cir. 1981). KHS&S challenges the ALJ’s finding that it s violation of § 1926.453(b)(2)(iv) was serious. We will uphold the ALJ’s finding if it was suppor ted by substantial evidence. See F & H Coatings , 900 F.3d at 1221. The ALJ found as follows: If Ruiz [Moya] or Rojas had slippe d while working from the aerial lift guardrails, they could have been se riously injured. The self-retracting lanyard, or yo-yo, they were connected to would quickly slow the rate of the fall or swing, but would not prev ent it. Complainan t and Respondent disagreed on the distance that the empl oyees would fall or swing if they lost their footing while standing on the guardrails. Complainant argued they could have fallen as much as 14 feet before the fall protection equipment stopped them. Respondent argued it w ould have only been 2 feet of free fall. The Court finds that a slip, fall, or swing of even 2-3 feet by either employee, could have resulted in them striking the steel I-beam, the outside of the basket, or falling in between th e basket and the steel I-beams. This could have resulted in serious injuries , including head injuries or broken limbs. This is especially true cons idering the shaky, unsteadiness of the19 aerial lift basket as employees move d around. Citation 1, Item 1 was properly characterized as a serious violation of the Act. ALJ’s Dec. & Ord. at 10 (citations omitted). KHS&S argues that no evidence supports the ALJ’s finding. It contends that the yo-yos the employees used would permit no more than a one-to-two-foot fall, which KHS&S argued “removes any fall hazar d.” Pet. Opening Br. at 27. KHS&S maintains there was no evidence supporting a finding that an employee could sustain the type of injuries assumed by the ALJ based on such a fall. We disagree. There was evidence that the employees were frequently standing on the railing of the aerial lift basket , which was only two inches wide, while installing sheets of drywall measuring fourfeet by eight feet that weighed forty pounds. The basket was uns teady and tipped toward one side when an employee stood on the railing. The basket was adjace nt to steel I-beams on the building, and the employees sometimes stood on both the rai ling and an I-beam to install drywall. The ALJ found that a slip, fall, or swing of even two feetcould cause an employee to strike a steel I-beam or the outside of the basket, which could resu lt in a head injury or a broken limb. The ALJ’s finding of a serious violation is supported by substantial evidence.
III. Conclusion We deny the petition for review and affirm the Commissioner’s decision.

Entered for the Court Bobby R. Baldock Circuit Judge