"(This approach implies that a sinner who does complete Teshuvah for his sin will not be found guilty by Beis Din, which is a problematic implication. See further discussion on the matter in Insights to Makos 13:2.)"
where do you see it's taluy on Teshuva according to the aruch laner, avadeh like the mahrasa on amud alef, its that daven that do teshuva, but according to oruch laner doesn't mention teshuva- power of his teffila alone! like we find in Navi, teffila can help w/o teshuva.
yaakov, NY
I have not yet had time to look properly into this question but my initial reaction is to say that the only time that we find that Tefilah helps without Teshuvah is what the Zohar says that Noach should have prayed to save the people in his generation from the Flood. This implies that Tefilah would have helped even though the people did not do Teshuvah.
Otherwise, the Gemara Zevachim 7b states that if somebody brings a sacrifice but has not done Teshuva this is described as "The sacrfice of the wicked is an abonimation" so I should have thought that the same applies to Tefilah without Teshuvah.
Ths would seem to be similar to the Gemara Taanis 16a where Rav Adah bar Ahavah said that if a person who has a transgression in his hands, confesses but does not abandon the transgression, this is comparable to someone holidng a Sheretz in his hand. He could immerse in every single Mikvah in the world but Hash-m will not forgive him.
However, these are initial reactions but I have not yet looked properly into the topic.
KOL TUV
Dovid Bloom
Follow-up reply:-
I have now looked more properly into this, bs'd. I still believe that the simple way of approaching this question is to say that that Tefilah without Teshuvah cannot bring forgiveness for the sinner, but I had an idea to support your question, Yaakov.
This is based on what I saw, bs'd, that Rav Elchonon Wasserman, hy'd, writes in Kovetz Ha'oros on Yevamos 67:13.
He cites Shevuos 13a that somebody who is liable for a Korban Chatas is not forgiven if he does not do Teshuvah. The problem is that Rabbi Meir says; Yevamos end 87b; that if 2 witnesses say to someone that he ate forbidden fat and he denies this he still must bring a Korban. Now, if he says that he did not eat it, he will not do Teshuva on it, but he still has to bring a Korban, which seems to prove that a Korban can help without Teshuva.
Rav Elchanan solves this riddle by writing that the reason that a Korban is usually worthless without Teshuvah is because if he did not do Teshuvah he is a Rasha and the Korban of a Rasha is an abonimation, as we saw above in the first answer in the name of Zevachim 7b. But if he genuinely does not think that he ate the fat he is not a Rasha. Rather, Rav Elchonon describes him as Shogeg. Therefore the Korban can help him attain Kapara even if he really did eat it.
Now back to the Oruch LaNer. Golus for killing is only if it happened beShogeg. I argue (to support your question, Yaakov) that it is possible that if somebody killed inadvertently it could be that he believes he has not sinned. He believes that the death of his victim was one of those unhappy accidents and does not appreciate that he should have been more careful and not inadvertently do something potentially dangerous that might lead to another's death. He is Shogeg so the prayer of the Kohen Gadol is able to atone for his sin, in the same way that according to Rabbi Meir a Korban can atone for eating Cheilev beShogeg.
Yasher Koach
Dovid Bloom
A justification of what we wrote:-
I had the following idea to suggest where we see Teshuva mentioned in the Aruch LeNer.
This is based on the Gemara Sanhedrin 37b which says "Golus Mechaperes Ovon"; exile is an atonement for Aveiros. The Rambam; Hilchos Teshuva 2:4; writes that exile atones for sin because it causes a person to be submissive, humble and weak of spirit.
So since someone went to Galus we can assume that he did Teshuva which is why Aruch LeNer did not mention Teshuva since it is automatic.
Dovid Bloom
We do not find that Teshuva is a necessary condition in order to receive atonement from Golus:-
I just spoke to a distinguished Talmid Chochom and he agreed that one does not have to say that it is essential that the inadvertent murderer must do Teshuvah in order to receive Kaporo from Golus. The Gemara Makos 2b does indeed tell us that it is a Kaporah for the Rotzeach beShogeg to go to the refuge city, but it may be that the exile itself gives him Kaporah even without Teshuvah.
I stand by what I wrote in my very first answer that a person cannot pray effectively for himself without doing Teshuvah, but there may be a possibility that the Tefilah of somebody else (in this case, the Kohen Gadol) for him could be effective without Teshuvah, as we find with Noach and the generation before the Mabul.
Good Shabbos
Dovid Bloom