Sighhhhhhhhhhh. No. Another misrepresentation. Once more, with feeling:
"My method" would have STARTED with Lumumba coming to the police station by 06.30 to be interviewed under caution (assuming he agreed to such a course of action, otherwise he'd have been arrested). Incidentally, he'd have been under the watchful eye of the police ever since the knock on his door at 06.00. On arrival at the staion, he would then have been asked about his whereabouts on the murder night, including any potential alibis, and about the content and meaning of the text message. He could also have been asked to volunteer samples of his blood, DNA, fingerprints, hair (head and genital), fingerprint, palmprints and footprints. If he'd refused to provide these samples, he could have been arrested.
If Lumumba had given the police an easily-verifiable alibi, and had also satisfied them in other areas, then he could have been told he was free to leave the station.
If he'd given them a more nebulous or hard-to-check alibi, and/or he'd provided indeterminate answers to other questions including those about the text message, he could have been asked to remain at the police station under caution while these things were investigated further. If he'd refused, he could have been arrested in order to guarantee his continued custody.
If he'd offered no alibi, or had an unverifiable alibi, and/or had given contradictory/evasive/dishonest answers to other questions, and/or if other evidence had came to light, he could have been arrested there and then.
Where, under my scenario, is there a possibility for Lumumba - if he had been culpable - to destroy evidence, intimidate witnesses or kill again?? If Lumumba HAD been the killer, he would clearly have been unable to provide the police with a verifiable alibi, and it's most likely that he'd have raised more suspicions in the interview. But the lack-of-verifiable-alibi factor in and of itself would have placed Lumumba under arrest and in custody in my scenario, without him ever leaving the police station after 06.30 on the 6th.