As pointed out, the Company Muster Rolls do indicate that L. L. Britt was captured on July 1, 1863. However, these reports are for months of 1864, well after the Battle of Gettysburg.

Most of the men of Company I that were captured in July 1863, were captured during the retreat on July 4th or 5th. Most of the men of Company I that were captured during the fighting on July 1, 1863, were "liberated" later in the day, when the Confederates routed the Federal troops through the town of Gettysburg.

L. L. Britt is listed as having been captured on July 5, 1863, at South Mountain, taken to Harrisburg, Pennsylvania, and then forwarded to Philadelphia on July 7, 1863.

The following is from "Retreat From Gettysburg" by Kent Masterson Brown:

The 4500 cavalrymen under Union General Judson Kilpatrick attacked the trains of the retreating Confederates near Monterey Pass. It was a running fight and as the charging Union cavalrymen galloped through the trains, they turned down the turnpike towards Waynesboro, past the tollbooth, forcing Confederate wagons and ambulances off the road and down the ravines on the west side of the mountain. The rainstorm seemed to intensify. The thunder and lightning coupled with the small arms and artillery fire and the yells and screams of the attackers, defenders, and the wounded, as well as the neighing of horses and mules, bellowing of cows, and bleating of sheep added an “inconceivable terror to the scene,” wrote an eyewitness.

Not long after midnight, Kilpatrick’s troopers struck the ambulance trains of Rodes’ Division on the summit of the mountain. The trains had been suddenly stalled by the breakdown of a quartermaster wagon of the 30th North Carolina in the train of Ramseur’s Brigade down near Waterloo. As the Union cavalrymen galloped down the turnpike toward Waterloo, they overwhelmed ambulance after ambulance and wagon after wagon until they hit the very rear of the quartermaster train of O’Neal’s Brigade, capturing ten wagons, including the brigade headquarters wagon, which had been captured from General Milroy’s fleeing troops at Martinsburg two weeks earlier and was being pulled by horses impressed in Pennsylvania until it had broken down in the road.

About 30 men from the 5th Alabama Infantry Regiment were captured by Kilpatrick's troops at that moment.