Must Kriyas Shema be said together with its brochos?

If a person recited Kriyas Shema before davening, he should still repeat it when he says the Birchos Kriyas Shema. Doing so fulfills the Talmudic mandate to learn Torah before Shemoneh Esrei. In addition, there are opinions which hold that one can only fulfill Kriyas Shema properly when it is recited together with its brochos. The poskim disagree about whether it is necessary to repeat Kriyas Shema if doing so would cause him to miss tefillah b’tzibur.

סעיף ב, ס"ק ד, וביה"ל ד"ה ונראה; ביאורים ומוספים דרשו, 4

Is intent necessary for a mitzvah?

The Gemara records a disagreement about whether mitzvos tzrichos kavanah--whether a person can only be yotzei a mitzvah if he intends to do so. For example, would one who is blowing a shofar (on Rosh Hashanah) for musical enjoyment be yotzei the mitzvah? The question would also arise if a person was reading the pesukim of Kriyas Shema during the time of Kriyas Shema but was not attempting to be yotzei the mitzvah. All opinions agree that if one thought he was exempt from the mitzvah at the time he was doing the mitzvah and then realized his mistake, he is not yotzei. For example, one who shook a lulav on Sukkos while thinking that it was Erev Sukkos would not be yotzei the mitzvah of daled minim.

סעיף ד, ס"ק ז-ח, וביה"ל ד"ה יש

Is kavanah necessary when eating matzah?

All opinions agree that a misasek--one who does a mitzvah without even intending to do the action--is not yotzei the mitzvah. For example, one who is blowing near the opening of a shofar without intending to emit a sound is not yotzei even if a blast comes out. In contrast, many opinions hold that one can be yotzei mitzvos which are done by eating even if he does not intend to do the mitzvah. All opinions agree that one does not fulfill a mitzvah if he has explicit intent not to be yotzei.  

ביה"ל ד"ה יש וד"ה ויש

• Shulchon Aruch rules that one should not answer Amen when the chazan finishes the brocha of Ahavah Rabba (Ahavas Olam). As in the case of a classic brocha over a mitzvah, where it is forbidden to interrupt between the brocha and the fulfillment of the mitzvah, interrupting between Ahavah Rabbah and Shema is problematic.

• Rema maintains that one should answer Amen to Ahavah Rabba. In his view, the brochos of Kriyas Shema are not brachos on the mitzvah of saying Kriyas Shema.

• The Gemara mentions two opinions about whether the brocha before Kriyas Shema should start with Ahavah Rabba or Ahavas Olam. Communities which follow minhag Ashkenaz say Ahavah Rabba in the morning and Ahavas Olam at night.

• Is kavanah necessary for a mitzvah mid’rabonon?

• Can circumstances demonstrate intent?

• What intent is necessary when saying the first pasuk of Shema?