MS too had many many "I don't know"s as well that impacted his credibility on the stand. MS couldn't remember anything that may have incriminated himself yet had the memory of an elephant when anything pointed to DM being responsible. Both MS and DM shy away from the inconvenient truth, IMO because they both know that they are both guilty but are only interested in saving themselves from punishment.
I think that they each went directly into self-protection mode the minute they were caught. DM in the beginning likely relied on his family name and reputation to protect him from jail, as I think he thought he could convince the police - or his lawyer at least - that DM had been taken advantage of and was being framed by someone already known to police, someone with a criminal record - MS. How convenient for DM had the police fallen for his story, but how naive and out of touch with reality was DM that he would think the police would believe him and overlook all the evidence that pointed directly at him.
I think MS went into paranoia mode immediately after DM's arrest for first degree murder and his paranoia only increased once DM's lawyer alluded to other suspects and a framing aspect that the lawyer could not discuss. With all communication cut off between DM and MS they had no way to brainstorm their next steps to try and help each other. Now they were each on their own. MS would never have gone to the police or a lawyer had he not been arrested, IMO. MS likely obsessed day and night from the time DM was caught until his own arrest about what DM was telling police and his lawyer. Paranoia and trust don't go together so I think once MS was arrested his paranoia won out and he was quickly convinced that DM had talked and had blamed MS for TB's murder. Of course MS would dig his heels in and set out to blame everything on DM. I think that even today they think the other betrayed them and neither seems to grasp that the only true betrayal of trust in the story was experienced by TB and SB who believed them when they said they wanted to test drive TB's truck with an interest in buying it. That was the most offensive betrayal in this scenario. An innocent life lost and trust in the good intentions of strangers now forever suspect.
When I look at the lives of DM, at 27 years old and MS, at 25 years old at the time TB was murdered, I see clearly that neither accused took any responsibility for their own actions. Neither had any real plan for their lives that didn't include some level of criminality and avoidance of adult responsibility. They each used the other to escape from responsibilities and their connection was not deep and meaningful, it was useful. Their friendship was simply born out of DM's casual need for weed and MS's ability to sell it to him. In MS's mind, DM had money to burn, party houses to flop in, a hangar with vehicles complete with his own personal mechanic, a penchant for thrills, an eye for the ladies, a superficial charm, an ambition for thievery, a fascination with guns and drugs and power, and DM had all the time in the world on his hands to play at his particular lifestyle. How impressive was DM and alluring to someone like MS who had no true ambition at all as he idled his life away daily while using and selling weed to his neighbourhood pals, drinking and smoking away the long boring hours of every similar day with others who were equally void of excitement for life, equally adrift, equally short on confidence and without much hope for a better future, a future that was frightening in its lack of potential and promise for MS. I believe MS writing rap lyrics was an outlet to express his frustrations, his inner feelings of uselessness, impotency and despair. And then DM came along and MS suddenly saw a way to a dream and a purpose. DM had the means to help MS become a rapper and MS latched on to DM's encouragement of his budding talents. DM kept the promises coming for MS and though always just slightly out of reach of fulfillment, MS became hooked on hope.
For DM, MS ensured that he would always have an admirer in his midst, a constant companion to count on who would question nothing and believe in every word DM would feed him and MS was more than hungry, he was starving for hope. DM recognized MS's need and of course he exploited it for all it was worth. In MS, DM found someone who also had nothing much to do all day and all day to spend with DM whenever DM needed a friend. An only child, a child who was viewed as an outcast, DM bought friends all of his life but not all were as simpatico, aimless and accommodating as MS. MS was available and eager to play second fiddle to DM and that was a big ego boost for DM whose soul was empty and needing a fix of adulation on a daily basis to keep him going. DM needed MS. Whatever story DM concocted, whatever wild mission he planned, MS was enthralled with DM's bravado and bold vision and MS was only too happy to play a starring role in a DM production. Each was lost in their own individual states of loneliness and inertia and each became lost to the world when together they chose to become the ultimate outsiders and end the dreams of others who did have hope and a future beckoning brightly on the horizon. In the end, DM and MS were much more alike than different. Even now, they are both looking for a plan to escape justice by blaming each other when the truth is they have only themselves to blame.
DM and MS made a choice together to commit theft and murder. It was a conscious choice and though neither is prepared to accept responsibility for the part they played, soon they will be on the other side of forcible confinement when the Crown convinces the jury that they are both guilty as charged and then they will be forced to accept the fate they created together for themselves. TB's final moments were tragically and mercilessly hopeless as he had no chance to escape, and now I hope that DM or MS have no hope to escape justice.
All MOO. All of the above is my own opinion and speculation.