Well, DH is a witness. What he hears, or sees, it testimony, but as any human testimony, it may be imprecise. Besides, unless it has been refuted, there is media evidence. 1) KA biking next to MW’s place of stay the day before murder - I guess it is on camera? Why? 2) KA’s case in direct vicinity of MW’s house at the time of the murder, 3) KA reaching MW on phone messaging to tell that she was living in CS house, 4) (not media, but worse than media, as executed with violation of laws) KA, essentially, becoming a fugitive almost immediately after the conversation in the police department.
After that, i have to be hard-pressured to be convinced that there was another person, and case of mistaken identity. If KA happened to be, by poor luck, in the vicinity of the murder at the time of the murder, she is a valuable witness, and should behave like such, not leave the country on her sister’s passport and do plastic surgery not to look like herself.