Perfect and Eternal

It is frequently stated that the Bible, is perfect, eternal, and as true today as when it was written.

I have one rebuttal to that. It needs only one.

Deuteronomy 21:1-9:

1 "If a slain person is found lying in the open country in the land which the LORD your God gives you to possess, and it is not known who has struck him,

2 then your elders and your judges shall go out and measure the distance to the cities which are around the slain one.

3 It shall be that the city which is nearest to the slain man, that is, the elders of that city, shall take a heifer of the herd, which has not been worked and which has not pulled in a yoke;

4 and the elders of that city shall bring the heifer down to a valley with running water, which has not been plowed or sown, and shall break the heifer's neck there in the valley.

5 Then the priests, the sons of Levi, shall come near, for the LORD your God has chosen them to serve Him and to bless in the name of the LORD; and every dispute and every assault shall be settled by them.

6 All the elders of that city which is nearest to the slain man shall (B)wash their hands over the heifer whose neck was broken in the valley;

7 and they shall answer and say, 'Our hands did not shed this blood, nor did our eyes see it.

8 Forgive Your people Israel whom You have redeemed, O LORD, and do not place the guilt of innocent blood in the midst of Your people Israel.' And the bloodguiltiness shall be forgiven them.

9 So you shall remove the guilt of innocent blood from your midst, when you do what is right in the eyes of the LORD.

Really, I don't know why we bother with police, courts, jails, and the entire criminal justice system, when we have this eternal, perfect piece of sleuthing to guide us.