How did Galad find out about Morgase?

Question

At the beginning of WoT Book 11, "Knife of Dreams", Galad Damodred challenges Eamon Valda to a duel in retribution for

the murder and rape of his step-mother, Morgase Trakand.

The rumor of murder was well-known by the time, but very few people (at most the five with her at the time, and likely only two of them) knew about her treatment at the hands of Eamon Valda, although Galad clearly makes reference to her "abuse" as well as murder:

“A Child of my command charges another of the Children with abusing a female relative of his, and claims the right of Trial Beneath the Light, which by law you must grant or deny.”

This begs the question, how did Galad find out about Morgase's treatment while being held by Eamon Valda?

Answer 1

Other Whitecloaks have brought the testimony to him.

No one had been able to confirm that the woman he regarded as his mother was dead, yet it must be so. A dozen men were certain she had vanished from the Fortress of Light before it fell to the Seanchan, and as many testified she had not been free to leave of her own will. Knife of Dreams, Prologue [emphasis added]

Indeed, it seems to be common knowledge around the Fortress of Light, although Morgase's maids do a reasonable job covering up for her, at least among her own followers:

"[Gill and Tallanvor] don't know, do they?" [...] "Lini and I drape linen over their eyes for you," Breane sneered, pulling her hand away. A Crown Of Swords, chapter 26

The "free will" part in the first quote is explained in A Crown of Swords as well, as Morgase realizes her cowardice in

sleeping with Valda out of fear of being beaten by the Questioners rather than out of pure political calculation.

And I can't imagine Valda doesn't brag about it to other Children; indeed, he uses it to try to enrage Galad further before their duel.