Why are dogs, sorcerers and murderers mentioned outside the New Jerusalem in Revelation 22?
The verse lists dogs, sorcerers, whoremongers, murderers, idolaters, and liars to show that none of them will be in the eternal state. They are already in their place, outside in the lake of fire, and will have no part in the glories of the eternal state.
Les explains that Revelation 22's list—dogs, sorcerers, whoremongers, murderers, idolaters, and liars—has thrown a curve at people and comes up periodically. He notes the same statement appeared in the previous chapter. His conclusion is that all that is implied is that none of these will be in the eternal state; they are already in their place, out in the lake of fire, and will have no part in the glories of the eternal state. He then connects this to verse 16, where Jesus sends His angel to testify these things in the churches. The word "churches" had been absent from Revelation since chapter 3 because the church was gone during the tribulation and had no part in it, but now in eternity the church again becomes prominent and part of the overall eternal economy. He also notes the repetition of the I Am.