Witt was captured in the assault on Port Hudson of May 27, 1863

NARA
1/8/63 Port Hudson, S O #11-Col Witt of the 10th Ark to report at once with his command-

1/13/63 The10th Ark arrives Port Hudson

3/31 Organization of troops in the 3rd Military Dist, Dept of Ms & East La, Gen Gardner
Buford bgde
27th Ala, Col. James Jackson.
49th Ala, Col. Jeptha Edwards.
4th Ala Bn,+ Lt Col. John Snodgrass.
6th Ala Bn, Lt Col. John Snodgrass.
10th Ark, Col. A. R. Witt.
3rd Ky, Col. A. P. Thompson.
7th Ky, Col. Ed. Crossland.
Miles' La Legion++
Boone's Btry++
Watson La Btry, Lt E. A. Toledano.

Southern Historical Society Papers. Vol. XIV. Pg. 305-325 Richmond, Va., January-December. 1886.
Fortification and Siege of Port Hudson--Compiled by the Association of Defenders of Port Hudson; M. J. Smith, Pres.; James Freret, Secretary
…
Anticipating an attack on Wednesday morning, [May 27th] …
This left Lieutenant-Colonel Locke's command in the same condition and strength as before. His line of battle was about a half a mile in advance of the Commissary Hill and the main line of works, and consisted of the following troops from right to left: A battalion of the Fifteenth Arkansas regiment, Lieutenant Colonel Lee commanding; Tenth regiment Arkansas volunteers, Colonel Witt; …

On Thursday morning, the 28th of May, a formal flag having been presented by General Banks and accepted by General Gardner, a cessation of hostilities was agreed upon until 7 o'clock, beginning at 12 M.
During this time the Infirmary Corps of each army was permitted to remove their dead or wounded from the field.
Two-thirds of the loss sustained during the siege of Port Hudson by the left wing occurred on this day. The casualties were almost entirely confined to the Tenth Arkansas, Colonel Witt--eighty (80) killed, wounded, and missing;

On the night of the 12th, [June] the troops were changed, so as to occupy permanent positions for the remainder of the siege. The following was the disposition of my command under this arrangement, from right to left:
Fifteenth Arkansas, Colonel Ben. Johnson; First Alabama, Lieutenant-Colonel Locke; Eighteenth Arkansas, Lieutenant-Colonel Parish; Tenth Arkansas, Lieutenant-Colonel Vaughan; Wingfield's (or the Company of Ninth Louisiana battalion cavalry, commanded by Lieutenant Daliet); Thirty-ninth Mississippi regiment, Colonel W. B. Shelby.

ROSTER OF CONFEDERATE FORCES ENGAGED IN THE DEFENCE OF PORT HUDSON, MAY 2IST TO JULY 8, 1863.
Major-General Frank Gardner commanding.
Left Wing, Right Resting on Railroad--J. G. W. STEEDMAN, Colonel Commanding.
Order of June 12th--…; Tenth Arkansas, Vaughn, Lieutenant-Colonel commanding; …

http://homepage.mac.com/netchemistwb/53rd_Mass_f/csa_porthudson.html
CSA Troops Present at the Surrender of Port Hudson
…
10th Arkansas, Maj. C. M. Cargile.

The Port Hudson Campaign: 1862-1863 By Edward Cunningham
…Shortly after dawn on Wednesday May 27th…Paine’s third brigade launched n attack on the 10th Arkansas…but the outnumbered Arkansans broke his assault…Colonel E L Vaughan’s 10th Arkansas…and they held

The Guns of Port Hudson, Vol II-David Edmonds

Weitzel’s Assault
Commisary Hill
May 27, 1863
Before too long, his troops had rounded up some 50 prisoners, mainly from the 10th Arkansas, among whom was Colonel A R Witt…

The Rebellion record: a diary of American events, with documents ..., Volume 7
Edited by Frank Moore
The First Alabama, Lieutenant-Colonel Locke, and the Tenth Arkansas, Colonel Witt, engaged the enemy outside the works, in the thick woods, and fought most gallantly, but were compelled by the heavy odds brought against them to fall back across the creek, and within the works. In this action Colonel Witt was captured, but was not fated to remain long a prisoner, being one of the daring band who affected their escape from the Maple Leaf, while on their way to a Yankee prison.