Can the גואל הדם kill the רוצח before the גמר דין?
In last week's parsha (מסעי) we had the dinim relating to a רוצח בשוגג. The question comes up can the גואל הדם kill the רוצח before the גמר דין?
At first glance it makes no sense, who says the guy is even guilty? However, the simple reading of the Gemara in Makos (10b) would seem to say yes.
This is actually a machlokes in the later acharonim. R' Shach (Avi Ezri Hilchos Rotzeach 5:9) states as a דבר פשוט that the גואל הדם cannot kill the רוצח before the גמר דין. After all, maybe he is פטור from גלות (e.g. קרוב לאונס). He explains the Gemara as saying that the גואל הדם can kill the רוצח after the גמר דין on the way to the עיר מקלט. The Chazon Ish (Likutim on Choshen Mishpat Siman 23) disagrees based on the Rambam (Hilchos Rotzeach 5:10) who seems to say that he can be killed even before the גמר דין. The Chazon Ish also brings a proof from the Gemara in Sanhedrin 49a (ע"ש). The Meiri also seems to say like this.
The קצות (Chosehn Mishpat Siman 2 Sif Katan 1) discusses a similar situation. He points out that by a רוצח במזיד without התראה or even שוגג קרוב למזיד, there is no psak din and yet the גואל הדם is allowed to kill the רוצח. We see from here that the גואל הדם can kill even without a גמר דין. On the other hand the קצות says that it doesn't make sense to say that he can be killed before the case even comes before בית דין, we haven't even established the facts. The קצות would seem to support the position of R' Shach that in the initial flight of the רוצח the גואל הדם would be prohibited from killing him because the facts have not yet been established. The Chazon Ish (based on the Rambam and Gemara in Sanhedrin) seems to disagree. The
Chazon Ish does not offer any סברה and his position seems very difficult, how can the גואל הדם kill the רוצח before the facts have even been established? Maybe he is not חייב גלות?