Is a narrator who makes many mistakes suitable for corroborating reports and for adducing as evidence?

The narration of a narrator who makes many mistakes may be suitable for corroborating evidence and supporting testimonies, or it may not be. A narration whose error has become apparent, or which is more likely to be denounced (munkar) or abandoned (matruk), cannot be strengthened. However, a narration that equally admits the possibility of being correct or incorrect can be strengthened, because it instills a strong presumption of its correctness. Imam Ahmad said: "Narration from weak narrators may be needed at times, but the denounced (munkar) is always denounced." If there is something that indicates the correctness of a narration from a narrator who makes many mistakes, it gains strength and can be strengthened, provided the narrator is known for truthfulness and trustworthiness. Ibn al-Salah (definition) clarified that the weakness of a hadith (definition) can be removed if it comes through multiple channels, provided the weakness stems from poor memory combined with the narrator's truthfulness, or from being a mursal (missing a direct link to the Prophet) hadith. However, it cannot be removed if the weakness is strong, such as when the narrator is accused of lying or if the hadith is anomalous (shadhdh). Ibn Hajar added that strengthening (jabr) depends on probability: what is equally probable can be strengthened, what is more likely to be rejected cannot be strengthened, and what is more likely to be accepted does not fall under this category, but rather belongs to the category of hasan (definition) li-dhatihi (good in itself).