If someone (eg sandek, mohel) is in Shul (the synagogue) whose presence stops the kehillo (congregation) saying tachanun, why is it that we do say tachanun in Selichos but not in davenning (the prayer service)?
There is no connection between Tachanun in Selichos to the regular Tachanun, as you can see that on Erev Rosh HaShana we say Tachanun in Selichos, yet we do not say Tachanun in Davening. The Tachanun we say by Davening is not said when there is a Sandek or mohel in the Shul, yet the Tachanun we say in Selichos, which has nothing to do with the Tachanun in Davening is said when there is a Sandak or Mohel in Shul.
1Agreed. But what is it about the Tachanun in Selichos that makes it special? Is it, as I saw somewhere (where?) that Selichos is a different "species" than Tefilloh and the exemptions only apply to Tefilloh. Do you know any relevant sources please? Oct 8, 2011 at 20:53
@AvrohomYitzchok I think Beurei Hatefilah addresses the origin of tachanun as part of Selichot, in one of its articles. I'll see if I can locate it. Most likely, it's in the High Holiday section.– DanFJul 7, 2017 at 21:21