My thoughts on this are as follows. The JWs always stress CONTEXT of a bible verse. Well lets look at the context. (the Revised Standard Version- I've highlighted verse 15)
Deut.19
[1] "When the LORD your God cuts off the nations whose land the LORD your God gives you, and you dispossess them and dwell in their cities and in their houses,
[2] you shall set apart three cities for you in the land which the LORD your God gives you to possess.
[3] You shall prepare the roads, and divide into three parts the area of the land which the LORD your God gives you as a possession, so that any manslayer can flee to them.
[4]
"This is the provision for the manslayer, who by fleeing there may save his life. If any one kills his neighbor unintentionally without having been at enmity with him in time past --
[5] as when a man goes into the forest with his neighbor to cut wood, and his hand swings the axe to cut down a tree, and the head slips from the handle and strikes his neighbor so that he dies -- he may flee to one of these cities and save his life;
[6] lest the avenger of blood in hot anger pursue the manslayer and overtake him, because the way is long, and wound him mortally, though the man did not deserve to die, since he was not at enmity with his neighbor in time past.
[7] Therefore I command you, You shall set apart three cities.
[8] And if the LORD your God enlarges your border, as he has sworn to your fathers, and gives you all the land which he promised to give to your fathers --
[9] provided you are careful to keep all this commandment, which I command you this day, by loving the LORD your God and by walking ever in his ways -- then you shall add three other cities to these three,
[10] lest innocent blood be shed in your land which the LORD your God gives you for an inheritance, and so the guilt of bloodshed be upon you.
[11]
"But if any man hates his neighbor, and lies in wait for him, and attacks him, and wounds him mortally so that he dies, and the man flees into one of these cities,
[12] then the elders of his city shall send and fetch him from there, and hand him over to the avenger of blood, so that he may die.
[13] Your eye shall not pity him, but you shall purge the guilt of innocent blood from Israel, so that it may be well with you.
[14]
"In the inheritance which you will hold in the land that the LORD your God gives you to possess, you shall not remove your neighbor's landmark, which the men of old have set.
[15]
"A single witness shall not prevail against a man for any crime or for any wrong in connection with any offense that he has committed; only on the evidence of two witnesses, or of three witnesses, shall a charge be sustained.
[16] If a malicious witness rises against any man to accuse him of wrongdoing,
[17] then both parties to the dispute shall appear before the LORD, before the priests and the judges who are in office in those days;
[18] the judges shall inquire diligently, and if the witness is a false witness and has accused his brother falsely,
[19] then you shall do to him as he had meant to do to his brother; so you shall purge the evil from the midst of you.
[20] And the rest shall hear, and fear, and shall never again commit any such evil among you.
[21] Your eye shall not pity; it shall be life for life, eye for eye, tooth for tooth, hand for hand, foot for foot.
Now tell me if the Jehovahs Witnesses are applying the WHOLE of that chapter, or are they using one verse? Why do they not follow the whole of the chapter?
Why do they not allow an "avenger of blood" to go and seek out murderers to kill them? Why do they not apply verse 21 where it says "eye for eye"?
If we look at our own justice system - we do follow Deut 19:15 in the sense that a criminal is not convicted without sufficient evidence and that usually involves more than 1 witness to a crime.
The watchtower are using this verse to justify their congregation arrangement which by their own admission is NOTHING TO DO WITH the justice system in place for the nations. (Hence their statement that elders should not get involved in worldly law). This is where they go wrong.
We cannot pick and choose from laws written for the nation of israel. The mosaic law is no longer applicable.
