Actually that's not the original scripture. Here's the original
Deu 19:15 One witness shall not rise up against a man for any iniquity, or for any sin, in any sin that he sinneth: at the mouth of two witnesses, or at the mouth of three witnesses, shall the matter be established.
Deu 19:16 If a false witness rise up against any man to testify against him that which is wrong;
Deu 19:17 Then both the men, between whom the controversy is, shall stand before the LORD, before the priests and the judges, which shall be in those days;
Deu 19:18 And the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and hath testified falsely against his brother;
Deu 19:19 Then shall ye do unto him, as he had thought to have done unto his brother: so shalt thou put the evil away from among you.
Deu 19:20 And those which remain shall hear, and fear, and shall henceforth commit no more any such evil among you.
Deu 19:21 And thine eye shall not pity; but life shall go for life, eye for eye, tooth for tooth, hand for hand, foot for foot.
You have to include the verses that explain the summation of vs19-21. It actually starts before v15.
Where do you see any modification by Jesus to this governing principle?
This is about how government prosecutes the accused and false witness.
Jesus didn't address this at all. He left it alone, you know why?
Mat 5:17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.
Mat 5:18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.
Mat 5:19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven.
Jesus addressed what was not address when this governing principle is found in scripture. Jesus addressed how the individual behaves.
Mat 5:39 But I say unto you, That ye resist not evil: but whosoever shall smite thee on thy right cheek, turn to him the other also.
Mat 5:40 And if any man will sue thee at the law, and take away thy coat, let him have thy cloke also.
Mat 5:41 And whosoever shall compel thee to go a mile, go with him twain.
Mat 5:42 Give to him that asketh thee, and from him that would borrow of thee turn not thou away.
He did not address how government prosecutes the accused and false witness.