Ulrich B. Philips, ("American negro slavery"), one of the most famous historian of slavery in USA, found 105 death sentences of slaves for sexual violences in Virginia only during the 80 years before emancipation (73 rapes and 32 attempts), on white women (two free colored excepted). Death was not the only sentence of course and the victim "reputation" was very important like the value of the guilty when slave.

It's possible to find some cases during the war involving slaves or free blacks :

• - On july 1862, two slaves, Stokes Martin and "John" was hanged in Chesterfield county (Va) for the rape of a white woman. ("Daily express" Petersburg, 16 july 1862)
  
• - On 24 march 1865, a slave called "Gillie" was hanged in Petersburg prison for the rape of a white lady. (Same newspaper, 25 march 1865)
  
• - A slave was hanged at Saltville (Va) for rape on the evening of  7 july 1863. "The execution was a lynching plain and simple" wrote a confederate officer in his diary ("Giles Buckner Cooke's diary", VHS)
  
• -"I never heard that the writ of habeas corpus was even spoken of, except in the case of a negro man who had attempted the rape of a white woman whose relations were in the army. The writ was not sued out and the negro was hanged, as he deserved to be." General Hindman (CSA) in his report on operations in trans-Mississippi in 1862. (OR SI vol XIII)
  
• -"I yesterday hanged a negro man, slave of William F. Smith, who, mistaking two of my men for the Abolitionists, hailed them across the creek, and volunteered to conduct them to the rebel camp, so as to surprise it; informed them of my strength and position, asked for a gun to kill his master, and said that he would knock down and rape any white woman." 8 april 1863, Deer Creek, Miss. , colonel Samuel S.Ferguson (CSA), (OR SI vol XXIV pt 1)
  
• - On 1st august 1863, "Abe", property of Mr Samuel H. Henry, raped Mrs Creger "white citizen and respectable Lady" of Blount county (Tennessee). "Abe" was hanged by Union justice with Lincoln's approval.
  
• - In 1862, after the arrival of McClellan's army in Peninsula, a black named "Lightfoot" went to the house of a white family. He convinced them that the general want to see all them , then tied them to trees and raped the women. He was tried by military court-martial and found guilty but escaped. (Calvin Mehaffey to mother, may 11 1862, C.Mehaffey letters SCHOFF CW library)
  
• -Alfred Locke, free man, colored, was heard by a military commission ar Salisbury(NC). Roseann Hendrick testified that during the night he broke down the door of Mrs Mary Sloan's house, jerked Mrs Sloan ou of bed and beat her : "he got her chocked down and just went to ravishing her". The court sentenced him to be hang with Lincoln's approval but Locke escaped his execution.
  
• On 25 may 1863, Hattie Motley, from Autauga county, Alabama, write to CS secretary of war, James Seddon, for her fear of slaves without white supervision. She speak about a rape committed by  "a negro brute" on the daughter of a prominent attorney which had spread panic among the female population.