Is there a difference if one slept before or after midnight?[1]
Practically we rule that whenever one has slept during the night for 60 breaths, whether before or after midnight, the evil spirit resides and he is required to wash his hands. Nevertheless the blessing is only recited after midnight as will be explained in the next Halacha.
[1] Practically the Poskim do not differentiate in this matter and one washes his hands with a blessing in all cases that one slept at night. [Piskeiy Teshuvos 1:6; See Kaf Hachaim 4:4; 48; 52-53] Nevertheless according to Admur the blessing is delayed until midnight.
Other Opinions regarding if one slept after midnight: Some write that the evil spirit only resides on one’s body if he is sleeping during midnight and hence if he went to sleep after midnight and after saying the morning blessings, he is not required to wash and certainly no blessing is said. [Divrei Shalom 48, grandson of Rashash in name of Rashash, brought in Kaf Hachaim 4:4 and 52; Ben Ish Chaiy Toldos 13; Shulchan Hatahor 4:10] The Ben Ish Chaiy ibid and Kaf Hachaim 4:48 conclude that one is to wash without a blessing if he went to sleep past midnight and already recited the morning blessings. The significance of the morning blessings is that it draws down an extra radiance of Divine light, hence exempting from needing to wash. If he did not yet recite he morning blessings then he is to wash with a blessing. [ibid] If however he slept before midnight and woke up before midnight the Ben Ish Chaiy ibid rules he is to wash with a blessing even before midnight.