A Mourner and Those Occupied With a Deceased Person are Exempt from the Recitation of the Sh'ma - containing 7 S'ifim
One who's relative died, for which he is required to mourn for them: even if it is not his responsibility to bury them, he is exempt from the recitation of the Sh'ma and from Tefilla [i.e. the Amidah]. And even if he wants to be strict with himself and to recite [it], he is not permitted [to do so]. But if one has someone who will take care of the needs of the burial for him, and he wants to be strict with himself to recite it, we do not protest against doing so [and see Yoreh Deah 341].
When does this apply? Regarding weekdays, but on Shabbat, one is obligated all day until evening if they are waiting until night at the [edge of the Shabbat] boundary to busy themselves with the needs of the burial [immediately after Shabbat]. But if one is not waiting until night at the boundary, they are obligated also at evening time. And [regarding] the second day of Yom Tov, its rule is like an ordinary day (and see Siman 548:5). And on the first day of Yom Tov, if one wants to bury [the dead] during that day, by means of non-Jews, then its rule is like a weekday, and if one does not want to bury him on that day, its rule is like Shabbat.
The one who watches the deceased, even if it is not one's own deceased is exempt.
If there were two watchers, this one watches and this one recites [the Recitation of the Sh'ma], and afterwards this one watches and this one recites.
The gravedigger for the deceased is exempt.
If there were 2 or more gravediggers, then all that are required for the needs of the digging at one time are exempt. And if there are additional [gravediggers], they slip away, recite, and return, and then busy themselves [with the digging], and the others slip away and return (see Yoreh Deah 365)
It is forbidden to recite the Recitation of the Sh'ma within 4 cubits of the deceased or in a cemetery, and if one recites, one has not fulfilled one's obligation.