I don't have the book with me here at hand, but the Society says that Judas was never present at the Lord's evening meal. Perhaps Blondie will have the exact text, but in the Insight Book, under Judas Iscariot, the Society say that Luke's account is not in chronolgical order and this proves Judas was not there. They say it would not be fitting for Judas to partake of the emblems.
But if you read Matthew, Mark and Luke's account, Judas is present there, and even asks Jesus if he is guilty of betraying him.
John's account reads slightly differently, but after the meal, Jesus washes the disciples feet, including Judas, and then tells Judas to "get done quickly" whatever it is he is going to do.
Let's look at all four accounts
Matthew 26
17 (20) Now on the first day of (21) Unleavened Bread the disciples came to Jesus and asked, "Where do You want us to prepare for You to eat the Passover?"
18 And He said, "Go into the city to (22) a certain man, and say to him, 'The Teacher says, " (23) My time is near; I am to keep the Passover at your house with My disciples."'"
19 The disciples did as Jesus had directed them; and they prepared the Passover.
The Last Passover
20 (24) Now when evening came, Jesus was reclining at the table with the twelve disciples.
21 As they were eating, He said, " (25) Truly I say to you that one of you will betray Me."
22 Being deeply grieved, they each one began to say to Him, "Surely not I, Lord?"
23 And He answered, " (26) He who dipped his hand with Me in the bowl is the one who will betray Me.
24 "The Son of Man is to go, (27) just as it is written of Him; but woe to that man by whom the Son of Man is betrayed! (28) It would have been good for that man if he had not been born."
25 And (29) Judas, who was betraying Him, said, "Surely it is not I, (30) Rabbi?" Jesus said to him, " (31) You have said it yourself."
The Lord's Supper Instituted
26 (32) While they were eating, Jesus took some bread, and (33) after a blessing, He broke it and gave it to the disciples, and said, "Take, eat; this is My body."
27 And when He had taken a cup and given thanks, He gave it to them, saying, "Drink from it, all of you;
28 for (34) this is My blood of the covenant, which is poured out for (35) many for forgiveness of sins.
29 "But I say to you, I will not drink of this fruit of the vine from now on until that day when I drink it new with you in My Father's kingdom."
30 (36) After singing a hymn, they went out to (37) the Mount of Olives.
Here, Judas has to be present at the evening meal, otherwise Jesus couldn't have said that one of his disciples would betray him. Also, the scripture does state that Jesus was reclining with the twelve disciples. There is no mention of Judas leaving at this time.
Mark 14
The Last Passover 12 (12) On the first day of (13) Unleavened Bread, when the Passover lamb was being (14) sacrificed, His disciples said to Him, "Where do You want us to go and prepare for You to eat the Passover?"
13 And He sent two of His disciples and said to them, "Go into the city, and a man will meet you carrying a pitcher of water; follow him;
14 and wherever he enters, say to the owner of the house, 'The Teacher says, "Where is My (15) guest room in which I may eat the Passover with My disciples?"'
15 "And he himself will show you a large upper room furnished and ready; prepare for us there."
16 The disciples went out and came to the city, and found it just as He had told them; and they prepared the Passover.
17 (16) When it was evening He came with the twelve.
18 As they were reclining at the table and eating, Jesus said, "Truly I say to you that one of you will betray Me--one who is eating with Me." 19 They began to be grieved and to say to Him one by one, "Surely not I?"
20 And He said to them, "It is one of the twelve, one who dips with Me in the bowl. 21 "For the Son of Man is to go just as it is written of Him; but woe to that man by whom the Son of Man is betrayed! It would have been good for that man if he had not been born."
The Lord's Supper
22 (17) While they were eating, He took some bread, and after a (18) blessing He broke it, and gave it to them, and said, "Take it; this is My body."
23 And when He had taken a cup and given thanks, He gave it to them, and they all drank from it.
24 And He said to them, "This is My (19) blood of the (20) covenant, which is poured out for many.
25 "Truly I say to you, I will never again drink of the fruit of the vine until that day when I drink it new in the kingdom of God."
26 (21) After singing a hymn, they went out to (22) the Mount of Olives.
Again, all twelve are here, and Jesus is addressing all 12 where he says, "It is one of the twelve, one who dips with Me in the bowl."
Luke
The Lord's Supper
14 (10) When the hour had come, He reclined at the table, and (11) the apostles with Him.
15 And He said to them, "I have earnestly desired to eat this Passover with you before I suffer;
16 for I say to you, I shall never again eat it (12) until it is fulfilled in the kingdom of God."
17 (13) And when He had taken a cup and (14) given thanks, He said, "Take this and share it among yourselves;
18 for (15) I say to you, I will not drink of the fruit of the vine from now on until the kingdom of God comes."
19 And when He had taken some bread and (16) given thanks, He broke it and gave it to them, saying, "This is My body which is given for you; do this in remembrance of Me."
20 And in the same way He took the cup after they had eaten, saying, "This cup which is (17) poured out for you is the (18) new covenant in My blood.
21 " (19) But behold, the hand of the one betraying Me is with Mine on the table. 22 "For indeed, the Son of Man is going (20) as it has been determined; but woe to that man by whom He is betrayed!"
23 And they began to discuss among themselves which one of them it might be who was going to do this thing.
Once again, Jesus would not have said, "But behold, the hand of the one betraying Me is with Mine on the table. " straight after he did the bread and wine if Judas had not been there.
Finally we get to John....
John
The Lord's Supper 1 Now before the Feast of (1) the Passover, Jesus knowing that (2) His hour had come that He would depart out of this world (3) to the Father, having loved His own who were in the world, He loved them to the end.
2 During supper, (4) the devil having already put into the heart of (5) Judas Iscariot, the son of Simon, to betray Him,
3 Jesus, (6) knowing that the Father had given all things into His hands, and that (7) He had come forth from God and was going back to God,
4 got up from supper, and laid aside His garments; and taking a towel, He (8) girded Himself.
Jesus Washes the Disciples' Feet
5 Then He poured water into the basin, and began to (9) wash the disciples' feet and to wipe them with the towel with which He was girded.
6 So He came to Simon Peter. He said to Him, "Lord, do You wash my feet?"
7 Jesus answered and said to him, "What I do you do not realize now, but you will understand (10) hereafter."
8 Peter said to Him, "Never shall You wash my feet!" Jesus answered him, " (11) If I do not wash you, (12) you have no part with Me."
9 Simon Peter said to Him, "Lord, then wash not only my feet, but also my hands and my head."
10 Jesus said to him, "He who has bathed needs only to wash his feet, but is completely clean; and (13) you are clean, but not all of you."
11 For (14) He knew the one who was betraying Him; for this reason He said, "Not all of you are clean." 12 So when He had washed their feet, and (15) taken His garments and reclined at the table again, He said to them, "Do you know what I have done to you?
13 "You call Me (16) Teacher and (17) Lord; and you are right, for so I am.
14 "If I then, (18) the Lord and the Teacher, washed your feet, you also ought to wash one another's feet.
15 "For I gave you (19) an example that you also should do as I did to you.
16 "Truly, truly, I say to you, (20) a slave is not greater than his master, nor is (21) one who is sent greater than the one who sent him.
17 "If you know these things, you are (22) blessed if you do them.
18 " (23) I do not speak of all of you. I know the ones I have (24) chosen; but it is (25) that the Scripture may be fulfilled, ' (26) HE WHO EATS MY BREAD HAS LIFTED UP HIS HEEL AGAINST ME.'
19 "From now on (27) I am telling you before it comes to pass, so that when it does occur, you may believe that (28) I am He.
20 "Truly, truly, I say to you, (29) he who receives whomever I send receives Me; and he who receives Me receives Him who sent Me."
Jesus Predicts His Betrayal
21 When Jesus had said this, He (30) became troubled in spirit, and testified and said, "Truly, truly, I say to you, that (31) one of you will betray Me."
22 The disciples began looking at one another, (32) at a loss to know of which one He was speaking.
23 There was reclining on (33) Jesus' bosom one of His disciples, (34) whom Jesus loved.
24 So Simon Peter gestured to him, and said to him, "Tell us who it is of whom He is speaking."
25 He, (35) leaning back thus on Jesus' bosom, said to Him, "Lord, who is it?"
26 Jesus then answered, "That is the one for whom I shall dip the morsel and give it to him." So when He had dipped the morsel, He took and gave it to Judas, (36) the son of Simon Iscariot.
27 After the morsel, (37) Satan then (38) entered into him. Therefore Jesus said to him, "What you do, do quickly."
28 Now no one of those reclining at the table knew for what purpose He had said this to him.
29 For some were supposing, because Judas (39) had the money box, that Jesus was saying to him, "Buy the things we have need of (40) for the feast"; or else, that he should (41) give something to the poor.
30 So after receiving the morsel he went out immediately; and (42) it was night.
This passage says that Jesus, " 4 got up from supper, and laid aside His garments; and taking a towel, He (8) girded Himself." and then he washed the feet of the disciples. So, the Lord's evening meal had evidently ended, although we did have a quick snack afterwards, as Jesus identifies his betrayer as, ""That is the one for whom I shall dip the morsel and give it to him." After this point, Judas left.
If you have the insight book, notice that the Society says that God's word is not in chronological order!! I have no idea why they would even do this.
All scriptures taken from http://bible.gospelcom.net/