A and W (a former advocate) rob a bank. During the robbery, W shoots and kills a security guard and A injures a bank official. Later an argument over the loot ensues between A and W, and A shoots W in the stomach. A is charged with attempted murder and W is the state witness in this case. Obviously, the bank robbery comes up in this case and during cross-examination W makes several statements in which he implicates himself in the murder of the security guard. At no time does the presiding magistrate warn W of his right in terms of section 203 of the Criminal Procedure Act 51 of 1977. Some months later, W is charged with the murder of the security guard. Can the state in this murder case use the statements that were made by W during his testimony in the other case as evidential material against W? Fully explain your answer.