From a case where the authors were involved in 2011, the sample voice of Luis Tralcal are compared, suspect of terrorist threat, as qualified the Public Ministry obtained from a statement incriminating and hearing and the incriminating speech sample, extracted from a recorded meeting, held between Mapuches leaders and a delegate from the CONADI - in order to analyze scientifically whether they belong to the same speaker which would support the prosecution hypothesis or to different speakers which would support the defense hypothesis. For this, the likelihood ratio calculating method (LR) that allows the evaluation of the numerical difference of the comparing parameters selected from the samples of the suspect and offender under the probability that they belong to the same speaker and the probability that they belong to different speakers, considering the reference population. For comparison, the F2 of the phoneme /a/ of the samples in dispute were used in the light of two population reference types: the samples of 4 speakers present in the CONADI audio and then, the samples of 25 Mapuche speakers extracted from Internet. In both cases, the likelihood ratio results give support to the defense.