About 15 people said they saw the Blessed Virgin Mary appear in a great light flanked by St Joseph and St John at the gable wall of the Roman Catholic Church in Knock on the 21st August 1879. A lamb standing on an altar was also reported.

Mary Beirne who lived nearby was walking past the Church when she and a friend, Mary McLoughlin, raised the alarm that a vision was happening.

Recognised as reliable. She asked (according to Judith Campbell) Judith Campbell to come to the gable even though she should have been urged to stay with her dying mother. If true, Mary's testimony would not really indicate the vision was supernatural.  The idea is that a holy vision does not inspire anything unlawful.

The witnesses all supposedly provided testimonies about the vision.  Mary Beirne is considered to be the star witness and reading them all shows how she influenced what the others saw.
Mary Beirne says that McLoughin came to her house at 7.30 and stayed only a little while and left at 7.45 or 8. She claimed in her 1879 testimony that it was still bright then.
She said, "At the distance of three hundred years or so from the Church, I beheld, all at once, standing out from the gable, and rather to the west of it, three figures which, on more attentive inspection, appeared to be that of the Blessed Virgin, of St Joseph and of St John. That of the Blessed Virgin was life-size, the others apparently not so big not so high as her figure; they stood a little distance out from the gable wall."

She did not put the claim that the images moved like living beings into her testimony. Beirne's handwritten deposition shows she called them statues. The priests were anxious for the witnesses to testify that they saw they saw living beings and not statues. That she resisted this pressure shows that the entities did not look like they were alive.
She softened her original testimony in 1932 by saying they only seemed to stand out from the wall (page 48, The Apparition at Knock). She said in 1936 that if you went near the wall the images looked as if they were painted on it (page 51, The Apparition at Knock).
It is easy to think flat figures stand out from the wall when you are three hundred yards away from them. Why is she not sure if the others were life size or not? Doesn't match her claim that she saw them for an hour and a quarter.

She stated in her deposition that she saw little jets around the lamb that seemed to reflect a light source. That's as good a witness as that the rain affected the light source - a magic lantern? - as I ever read.

In 1880 she admitted to the Weekly News that there was good light. This was her response to the question if there was daylight at the time. As the weather had been so bad and it had been raining all day it could have been quite dark. Good light shows that it was not that bright after all.
She told the paper that she was going from the house to the chapel at 8 to lock it up (page 46, The Apparition at Knock). This was a lie as the chapel had been locked at 7.30 by her sister Margaret who lived in the same house. Why did she lie? If she went to lock the chapel, what was she doing going in the direction of the southern gable when the door to be locked was in the north?

Mary Beirne told a lie about going to lock the Church. Her later claim that the image was like a painting on the wall clothed in soft light like the moon gives us reason to think that the apparition was a natural occurrence. She was regarded as the best witness though there is much in her testimony to indicate that no true miracle took place. Obviously the investigators didn't notice that! This makes the testimonies to the magical side of it all to be questionable.
She said in 1932 that the light was like the soft silvery light of the moon (page 50, The Apparition at Knock). And she said it was not like any light she ever saw. Nobody could say that of anything that looked like moonlight. This is an indication that she was attempting to say that the light was magical and got it wrong and let the truth slip. It shows that somebody had been guiding her in what to say - she knew she wasn't supposed to admit that the light was like the moon.
In 1880, the book The Apparitions and Miracles at Knock.: Also, the Official Depositions of the Eye-Witnesses stated, "As some persons were hurriedly going along the road which leads to the chapel, at about 7-30 P.M., they perceived the wall beautifully illuminated by a soft, white, flickering Sight, through which could be perceived brilliant stars twinkling as on a fine frosty night."
A magic lantern would give off a soft light that would get brighter as night falls. And we do know that night was exceptionally dark!
In 1880, in an interview with the Weekly News she stated the following.
She claimed that three or four times since the apparition, she saw stars come out of the gable and form a light like the moon but she saw nothing else. She was prone then to seeing visions. Had she seen a crude light at the gable that stayed for a while it is easy to picture her getting carried away and thinking she saw people standing in the light.
She contradicted Bridget Trench by denying that the Virgin's feet were visible. That is important - the story that Trench tried to feel the feet of the Virgin is probably a lie. It makes a liar of Patrick Hill who said an old woman tried to touch the feet of the Virgin. Maggie Beirne and Mary were sisters and Maggie said the feet were visible meaning that Mary would only have denied this if she were sure.
A big thing was made of the old woman trying to kiss the Virgin's feet. It was a quaint thing that would stand out in the whole story. Psychologically, Beirne could not have forgotten it if it really did happen. If it didn't happen, then the believers cannot say, "If the images were made by a projector, anybody trying to touch them would have made a shadow." We must not forget the important point, that we do not know if a shadow was ever made. All the priest writing the depositions down had to do was ask questions phrased to avoid causing the witness to mention any shadow or if a witness did mention a shadow all the priest had to do was just leave it out. It would have reflected badly on the idea that the apparition was a miracle. There is no evidence at all against the possibility that a shadow was caused. Trench was unlikely to have tried to touch the feet or wondered why she couldn't feel them when the image seemed to go flat against the wall when approached. She may have lied when she said she tried this thing and wondered why the 3-d feet could not be felt. We can take the testimony as to the flatness as being true.
Thanks to Beirne, it was recorded in 1880 that the Archdeacon upon being told of the vision said it was a reflection from a stained glass window! Considering that the area was victimised by a culture of visions of fairies and holy virgins this scepticism is obviously feigned. The culture is verified in Knock The Virgin's Apparition in Nineteenth Century Ireland.
Beirne went to her own house after discovering the vision and her brother Dominick was in bed. She got him to go with her to look at it and they stood at the schoolhouse. He testified - "I then went with her, and by this time some ten or twelve people had been collected around the place, namely, around the ditch or wall fronting the gable, where the vision was being seen, and to the south of the schoolhouse". What were they doing at the schoolhouse? You don't stand that far away from an amazing vision! The interviewer asked her why so few saw the vision. She stated that she thought twelve people saw it. She claimed that they were so rapt in the vision that they never thought on telling other people. That was a lie for she was the one that did most of the running to get the word out. She even went to the house where people were sitting with a dying woman. And the visionaries that left surely must have told people.

The oddities show that the visionaries didn't want to look stupid and knew that what they saw might not actually be a real miracle.