"First degree murder is the unlawful killing of a human being with malice, premeditation, and deliberation." State v. Misenheimer, 304 N.C. 108, 113, 282 S.E.2d 791, 795 (1981). Premeditation and deliberation are mental processes that are difficult to prove and are usually established by circumstantial evidence. State v. Sierra, 335 N.C. 753, 758, 440 S.E.2d 791, 794 (1994). "To determine if a crime was with premeditation and deliberation, there must be evidence that a defendant thought about the act for some length of time, however short, before the actual killing; no particular amount of time is necessary to illustrate that there was premeditation." Id. Deliberation is a "fixed design to kill notwithstanding defendant was angry or in an emotional state at the time." State v. Ruof, 296 N.C. 623, 636, 252 S.E.2d 720, 728 (1979). Further evidence from which premeditation and deliberation might be inferred is the conduct of the defendant following the killing and the brutal manner in which the killing was done. Sierra, 335 N.C. at 758, 440 S.E.2d at 794. The Supreme Court has disavowed the rule that "the trial court is required to instruct on second degree murder in all first degree murder cases in which the State relies on the elements of premeditation and deliberation." State v. Hickey, 317 N.C. 457, 470, 346 S.E.2d 646, 655 (1986), (citing State v. Strickland, 307 N.C. 274, 290-91, 298 S.E.2d 645, 656 (1983) (overruled on other grounds)). So long as the evidence introduced by the State is "positive as to each and every element of the crime charged and there is no conflicting evidence relating to any element of the crime charged" the court is not required to give a second-degree instruction. Strickland, 307 N.C. at 283, 298 S.E.2d at 652.