Mary Ann,
When I see a note that says a man's last card was "Deserted", I feel a need to check further because I have seen this note many times only to find that he had joined another unit or his name was spelled differently. Look for others from the same area, possible transcription errors, or relatives. I have found files mixed before.

Read the regimental histories:

1st Miss. Cav. Reserve; 17th Battn. Cav.; 9th Miss. Cav.; Ferguson's Brigade (in Atlanta Campaign)[included, 9th Miss. Cav., 11th Miss. Cav.; 12 th Miss. Cav., 2nd Alabama Cav., 56th AL. Cav.)

I suggest that you get these records:

H. L. Pearson, "Poitevent's Company "B" (Hancock County) 17 Battalion Cav.
H. Pearson Co. G 1st Miss. Cav. Res.
L. Pearson "Roger's Company"
L. S. Pearson Co. K 1st Miss. Cav. Res.
E. S. Pearson Co. E 9th Miss. Cav.

It is likely that he served in other units before the 17th Battn Cav. was formed in Feb. 1863 and it appears that the 17th Battn. was a dismounted battalion in April-May 1863 as part of Steede's and Adams Cav. On May 3rd 1863 they were stationed at Jackson, Mississippi. Coincidentally he was listed as "deserted" two weeks later.

Maybe he got mad when they made him give up his horse. Who knows.

In any case, I am sure there is more to the story of Leander Pearson. Good hunting.
PS thanks for the link to the Pearson Cemetery. I had been looking for a tobstone for Eb Stewart Co. F 7th Miss.
Regards,