Utah Code § 34-25-2: "Fellow servant" defined.

All persons who are engaged in the service of any employer and who while so engaged are in the same grade of service and are working together at the same time and place and to a common purpose, neither of such persons being entrusted by such employer with any superintendence or control over the person's fellow employees, are fellow servants with each other; but nothing herein contained shall be so construed as to make the employees of such employer fellow servants with other employees engaged in any other department of service of such employer. Employees who do not come within the provisions of this section may not be considered fellow servants.