Abstract

Forensic authorship analysis is based on two assumptions: that every individual has a unique idiolect, and that features characteristic of that idiolect will recur with a relatively stable frequency. Yet, a speaker’s language can change with age, affective states, according to audience, or genre. Thus, studies on authorship analysis should adopt the theory that while some linguistic parameters of an idiolect can remain stable, others can change depending on various circumstances. This investigation, which takes a constructional and functional-based approach to discourse-level phenomena in idiolectal stability, analyzes cross-genre data produced by nine Mexican participants throughout a twelve-year time span. This study contributes to a greater understanding of the linguistic elements that survive genre effects and are potentially useful in both investigative and evidential forensic linguistic work. We provide a detailed description of linguistic features, their specific values, and context-dependent interpretation, keeping in mind the context of expert linguistic testimony, with its preference for methods which “employ linguistically motivated analyses in combination with quantitative tools” (Solan & Tiersma, 2004, p.463). Our findings show that idiolectal style tends to remain stable across genres and communication modes in epistemic modality constructions. Epistemic markers —specifically, markers indicating low commitment by the speaker (e.g., _no sé_ ‘I don’t know’) or expressing indirectness when introducing the illocutionary force (e.g., _la verdad [es que]_ ‘the truth [is that]’)— display idiolectal stability, as these markers seem to be the most effective in terms of allowing speakers to strategically manifest the extent of their knowledge regarding what is said.