“It has long been accepted that the defence of insanity, in Anglo American law, is unsatisfactory and in need of reform” (Hathaway, 2009, pg. 310). Since its emergence, the Not Guilty by Reason of Insanity defence has been proven to be most problematic and contentious. The premise of this research is to critically analyse this defence and discuss alternative approaches, primarily the Guilty but Mentally Ill verdict. In order to do so, this paper will discuss the limitations and problems affiliated with the insanity defence such as, misuse and abuse, inconsistency, and reliability. Many argue that the defence is remarkably outdated as it first originated in 1843. The discussed limitations illustrate the requirement for amendment of the insanity defence. The most recognised alternative approach is the GBMI verdict which was introduced following ample public vexation with the insanity defence. GBMI has not been adopted worldwide and is a relatively new statute. An important note regarding the GBMI verdict is that it is not intended to abolish the insanity defence, merely to evolve and improve the defence. It has been discerned that the GBMI has an abundant number of advantages, be that as it may, it still requires further research and work. This paper also acknowledges the possibility of the abolition of the insanity plea. In order to evaluate the benefits and downfalls of the elimination of the insanity defence, the Idaho case study is deliberated. The benefits and disadvantages of abolishing the defence will be discussed and analysed. On account of such, it will be concluded that eliminating a form of the insanity defence from the criminal justice system is not a viable option. Following the research conducted, it has been discovered that the United States has conducted the most reform and amendment on the insanity defence as it is the only jurisdiction to adopt the guilty but mentally ill approach and some States have even opted to abolish the not guilty by reason of insanity defence. The majority of cases in this paper are from instances in the United States. Ireland and the United Kingdom have very few examples of cases on the topic as they both predominantly follow the standard not guilty by reason of insanity ruling. Further findings of this paper demonstrate that the Not Guilty by Reason of Insanity Defence is in fact outdated and in need of reform, however the solution is not a simple fix, there is not one sole solution to reforming and improving the insanity defence.