I have explained this. There would be precious little point in adding BZ if they told everybody. Can you think why. You are a scientist.
BZ would be used as it has it likely has a similar spectrometry profile to the suspected agent.
Mass spectrometry - Wikipedia
Fourier transform mass spectrometry (FTMS), or more precisely Fourier transform ion cyclotron resonance MS, measures mass by detecting the image current produced by ions cyclotroning in the presence of a magnetic field. Instead of measuring the deflection of ions with a detector such as an electron multiplier, the ions are injected into a Penning trap (a static electric/magnetic ion trap) where they effectively form part of a circuit.
Detectors at fixed positions in space measure the electrical signal of ions which pass near them over time, producing a periodic signal. Since the frequency of an ion's cycling is determined by its mass-to-charge ratio, this can be deconvoluted by performing a Fourier transform on the signal. FTMS has the advantage of high sensitivity (since each ion is "counted" more than once) and much higher resolution and thus precision
Where have you read that BZ has similar 'spectrometry profile' to suspected chemical that was allegedly used as a poison?