28 CFR § 21.4 - Fees and allowances of fact witnesses.
(a) Fee. A witness shall be paid an attendance fee of $30 per day for each day's attendance. A witness shall also be paid the attendance fee for the time necessarily occupied in going to and returning from the place of attendance. However, if both attendance and travel occur on the same day, a witness is entitled to only one fee.
(b) Allowable transportation expenses. A witness shall be entitled to transportation expenses based on the means of transportation reasonably utilized (based on the nature, duration, location and distance of travel) and the distance necessarily traveled from and to such witness' residence by the shortest practical route and the fastest means of transportation available in going to and returning from the place of attendance. Additional costs incurred (including attendance fees and subsistence allowances) because of a slower means of transportation must be justified for consideration.
(1) A witness who travels by regularly scheduled common carrier shall be paid for the actual expenses of transportation at the most economical rate reasonably available. A receipt or other evidence of actual cost shall be furnished.
(2) A witness who travels by privately owned vehicle shall be paid a transportation allowance equal to the mileage allowance paid for official travel of employees of the Federal Government under the provisions of 5 U.S.C. 5704. However, when two or more witnesses travel in the same privately owned vehicle, only the witness incurring the expense shall receive the mileage allowance.
(3) A witness incurring incidental transportation expenses, such as taxi fares between the place of attendance, residence or lodging and the carrier terminals; bridge, road and tunnel tolls; ferry fares; and parking fees shall be paid in full for such expenses. Receipts or other evidence of actual payment are required for all parking fees (if available) and all other single items costing more than $25.
(4) First-class travel by witnesses requires the same justification and approval required for first-class travel by employees of the Federal Government.
(c) Subsistence allowance. A witness (other than a witness detained in custody) who is required to be away from his or her residence overnight is entitled to a subsistence allowance. A witness who is not required to be away from his or her residence overnight is not entitled to a subsistence allowance. The witness' subsistence allowance shall not exceed either the per diem rate or the actual subsistence allowance rate prescribed for Government employees for the place of attendance. These rates are established by the Administrator, General Services, for areas within the conterminous United States; the Secretary of Defense for areas of the United States other than conterminous; or the Secretary of State as published in the Standardized Regulations (Government Civilians, Foreign Areas) for foreign areas. The witness' subsistence allowance shall consist of a meal and miscellaneous expense portion and a lodging portion. When an overnight stay is required, the witness shall be entitled to:
(1) The meal and miscellaneous expense portion for each day (or partial day) the witness is required to remain away from his or her residence and
(2) The lodging portion for each night the witness is required to incur a lodging expense.
(d) Detained witness fee. A witness (other than an alien covered by § 21.3) detained in custody pursuant to 18 U.S.C. 3149 for want of security for his or her appearance shall receive subsistence in kind and shall be paid a single daily attendance fee for each day the witness is detained. A witness in custody for purposes other than 18 U.S.C. 3149 is ineligible to receive the attendance and subsistence fees provided by this section.