There were no Eye Witneeses to the Crucifxion

Muslims will claim that it was not Jesus who died on the cross, but Allah just made it appear that way.
 They will often say that all the disciples fled out of fear and so all the crucifixion accounts are hearsay.
Muslims have no consistent explanation as to who or what was on the cross.

However according to the Bible John was an eye witness:

³¹ Since it was the preparation day, the Jews did not want the bodies to remain on the cross on the Sabbath (for that Sabbath was a special day). They requested that Pilate have the men’s legs broken and that their bodies be taken away. ³² So the soldiers came and broke the legs of the first man and of the other one who had been crucified with Him. ³³ When they came to Jesus, they did not break His legs since they saw that He was already dead. ³⁴ But one of the soldiers pierced His side with a spear, and at once blood and water came out. ³⁵ He who saw this has testified so that you also may believe.
(John 19:31-35)

Earlier in the same chapter we read that his mother Mary was there also:

²⁵ Standing by the cross of Jesus were His mother, His mother’s sister, Mary the wife of Clopas, and Mary Magdalene. ²⁶ When Jesus saw His mother and the disciple He loved standing there, He said to His mother, “Woman, here is your son.” ²⁷ Then He said to the disciple, “Here is your mother.” And from that hour the disciple took her into his home.
(John 19:25-27)

Therefore Jesus directly identified himself to his mother and to John  his disciple