The categorical/modified categorical analysis is a judicial tool used by judges to enhance a sentence in a federal court criminal proceeding or determine the immigration rights of a non-citizen in immigration proceedings, in light of a prior state or federal criminal conviction, often entered pursuant to a guilty plea.
Many state criminal laws have unique or unusual provisions that differ from other state and federal criminal laws. Judges are concerned that federal consequences of prior convictions should be based upon uniform legal notions. Thus, an enhanced sentence for a federal crime or an immigration outcome should not depend on the fortuitous circumstance of the location (by state) where the prior crime took place and any legal eccentricities of its criminal justice system. The categorical/modified categorical analysis is used to determine whether a specific prior conviction matches a uniform definition under either federal law or generally accepted principles of criminal law according to academic and other respected sources. If it does not, then the prior conviction should be disregarded in the determination of a subsequent sentencing in the federal system, or an immigration proceeding. Otherwise, it must be taken into account in the current proceeding, either to enhance a federal sentence of a defendant or order removal of a respondent from the United States.
It may help to understand the process better by imagining a cooking competition between famous chefs; let us postulate that the broad category is oriental eggrolls. The cooking judges require each entrant to submit a written recipe of ingredients to them, in order to determine the proper category in which to place each contestant’s offerings. If two chefs have similar recipes, but one(Chef A)'s recipe includes a hot sauce, the ingredients of which are listed in the recipe, and another(chef B)'s recipe does not, there may not be a suitable match. Based upon the listed ingredients, there is a categorical mismatch between the entries if hot and spicy should be a separate subcategory. In such a case, the chefs will not compete against each other in the eggroll competition because they are not categorically matched against each other.
But suppose in reviewing chef B's non-hot recipe, a judge notices that the some of ingredients include unspecified “spices”. Could these unspecified spices make the eggroll sufficiently hot to create a categorical match? There is no way of knowing absent further information about the spices. It could be helpful to the judges if they had reliable information about the spices that are included in the otherwise seemingly non-spicy hot egg roll recipe of chef B. Not all information may be reliable, such as information obtained from a competitor or disgruntled former employee of Chef B, so the judges will want to be careful in the type of proof they require.If available, one relatively reliable source might be a recorded television program of chef B demonstrating the preparation of his eggrolls. In the course of the television program, assuming the spices were identified clearly to the viewer, the question could be resolved. If those spices rendered the eggrolls "hot and spicy", then based upon the written recipes as supplemented by the videotape, a modified categorical match would exist. The written recipes would not be a categorical match but with the videotape, there would be a modified categorical match, based on non-written sources, in which case, the chefs would nonetheless compete against each other in the same category. Matching the two recipes as written down and submitted to the judge is the "categorical" part of the analysis. Adding the videotape evidence is the "modified categorical" portion of the analysis.
Like the ingredients in the recipe, every crime has certain ingredients, called elements. If two crimes, one state and one federal, had identical elements, then they can be said to have a categorical match. However, it is rare that two crimes have identical elements, even if they intend to prohibit the same criminal conduct. So the judges first dissect the crime of the prior conviction into its elements, and compare them to the elements of an equivalent federal crime or generally accepted standard definition of academic and other respected legal sources to determine if there is a categorical match. If the crimes are similar but not identical, and one or more essential elements is missing, then the judges will look to a limited set of legal documents that were connected with the prior conviction, like the videotape in the recipe's example. Permissible documents from a prior conviction include the charging document( indictment or information), a plea agreement admitting guilt, or a transcript of an exchange between the judge and defendant in open court and on the record admitting the prior crime as a factual basis for a guilty plea, or statements made by a defendant at sentencing. Impermissible documents may include police reports or witness statements (because they may include puffing or sour grapes), and presentence reports, (unless unchallenged as to their facts by the defense prior to sentencing). The permissible documents are seen as likely reliable because of the procedural safeguards in place; the latter, somewhat unreliable because of potential biases of law enforcement and possibly overzealous prosecution of the case.