Each forensic PMHNP should possess theoretical and practical knowledge of the criminal justice and mental health systems. Forensically trained PMHNPs have a good knowledge base of the following:
* The functions of the court system
* Litigation procedures
* Workings of the criminal justice system
* Relevant case law and health litigation
* Mental health, distorted thinking patterns, and impaired cognition
* Safety, security, management, and risk assessment of individuals
The primary knowledge base of forensic PMHNPs does not include understanding the rights of the accused, nonverbal cues of the accused, or proper physical assessment of victims.

Evidence-based practice demands the use of the best knowledge. The evidence hierarchy ranks sources of knowledge according to the strength of the information they provide. The best evidence comes from Level 1 of the evidence hierarchy, which includes meta-analyses. All levels are listed below.
* Level 1 (strongest): Systematic review of randomized controlled trials or systematic review of nonrandomized trials
* Level 2: Single randomized controlled trial or single nonrandomized trial
* Level 3: Systematic review of correlational or observational studies
* Level 4: Single correlational or observational study
* Level 5: Systematic review of descriptive, qualitative, or physiologic studies
* Level 6: Single descriptive, qualitative, or physiologic study
* Level 7 (weakest): Opinions of authorities and expert committees

The Barnes Akathisia Rating Scale is a commonly used tool for evaluating the presence and severity of Akathisia, a condition characterized by inner restlessness and an urge to move. A score of 5-7 on the Barnes Akathisia Rating Scale indicates the presence of moderate to severe Akathisia.
A score of 0 on the Barnes Akathisia Rating Scale indicates the absence of Akathisia, while scores of 1-2 indicate mild Akathisia. Scores of 3-4 indicate moderate Akathisia. The nurse should consider the patient's symptoms and the results of the Barnes Akathisia Rating Scale when making a diagnosis of Akathisia and determining the appropriate treatment plan.

Hypomania is often characterized by restless, bright, oversexualized, and flamboyant dressing.
Patients with dementia may have inappropriate dressing, but this is not the characteristic appearance of a dementia patient. Depressed patients are more likely to dress in dark and loose-fitting clothing. Anxious patients are restless but often appropriately dressed.

Specifiers are special descriptions added to a patient's diagnosis to provide more information. Specifiers help characterize the condition and describe its overall course. Specifiers used to describe mood disorders include the following:
* With atypical features: These patients eat a lot and gain weight, sleep excessively, and have a feeling of being sluggish or paralyzed. They are also sensitive to rejection.
* With melancholic features: These patients feel worse in the morning than in the afternoon, and they experience decreased appetite, weight loss, and agitation. They also tend to feel excessively guilty and have trouble making decisions.
* With anxious distress: These patients have high levels of tension, restlessness, worry, and fear.
* With catatonic features: These patients exhibit either motor hyperactivity or inactivity.
* With mixed features: These patients are experiencing a mixture of both manic and depressive symptoms.
* With peripartum onset: These patients develop a mood episode during pregnancy or within a month of having their baby.
* With psychotic features: These patients develop delusions or hallucinations along with their mood symptoms.
* With rapid cycling: These patients have experienced at least four mood episodes in the past year.
* With a seasonal pattern: These patients regularly become ill at a certain time of the year.