In the 1980s the traditional Hippocratic term excited delirium was transplanted from the bedsides of febrile, agitated and disoriented patients to the streets of Miami. Deaths in custody of young men who were intoxicated with cocaine and who were restrained by the police because of their erratic or violent behaviour were attributed to excited delirium. The blood concentrations of cocaine in these subjects were approximately ten times lower than the lethal level and other factors which might have contributed to the fatal outcome, such as the police use of neck-holds, choke-holds or ‘hog-tying’, were relegated to a minor role compared with the reframed ‘diagnosis’ of excited delirium. Over the course of the next few decades ‘excited delirium’ might be applied to virtually any highly agitated person behaving violently in a public place and who subsequently died in custody while being restrained or shortly afterwards. Expert witnesses, mainly forensic pathologists, testified that the deceased's death was probably inevitable given the perilous nature of excited delirium, even though this diagnostic entity lacked any consistent neuropathological basis and depended entirely on observed behaviour. This history of the rise and fall of this disputed diagnosis is a partial response to the sociologist Phil Brown's 1995 paper asking who benefits, or at least avoids trouble, by the identification and use of a diagnosis.

The phase identification of a polycrystalline mixture by X-ray powder diffraction data is often requested for studying materials interesting to different scientific and technological fields: chemistry, pharmaceutics, mineralogy, archeometry, forensic science, etc. The availability of user friendly computer programs, able to carry out qualitative phase analysis in efficient and possibly automatic way, is extremely useful to the scientific community involved in powder diffraction. QUALX2.0, the evolution of QUALX, is a freely distributed software for qualitative phase analysis. Based on the traditional search–match method, it is able to manage both a commercial database (PDF-2 maintained by ICDD), and a freely available database (POW_COD generated by the structure information contained in the Crystallography Open Database). QUALX2.0 is continuously improved in terms of computing and graphic tools. Correspondingly, the database POW_COD is suitably modified to make efficient the operations of search. The search–match approach can be facilitated by the use of restraints, when available, involving the chemical composition, the kind of compound(s) (e.g., organic, inorganic, etc.), the symmetry (space group, crystal system), the unit-cell parameters and/or volume, the crystal properties (measured and/or calculated crystal density, crystal color). An outline of the main features of QUALX2.0 and an example of application is described.

We know a lot about normal values of bond distances, bond angles, torsion angles, and other molecular parameters. This knowledge can be incorporated into the structure solution process and into Rietveld refinement through the use of restraints and rigid bodies. An important measure of the quality of the refined model is the chemical reasonableness of molecular geometry. Refinement of the structures of calcium tartrate tetrahydrate and guaifenesin is used to illustrate the importance of chemical reasonableness in determining the quality of a Rietveld refinement.

Besides statistical and graphical measures, many structural features can be used to assess the quality of a Rietveld refinement. These include the metric symmetry of the lattice (which can assist in determining the true symmetry and in identifying isostructural compounds), bond distances and angles (which should fall within normal ranges), displacement coefficients, refined stoichiometry, the absolute values of the standard uncertainties of the fractional coordinates, the hydrogen bonding pattern, the presence of approximate symmetry, the presence of unindexed peaks in the pattern, and whether the refinement converges at all. Chemical knowledge can be built into a Rietveld refinement though the use of restraints and rigid bodies. A knowledge of chemical reasonableness proved important in refining the correct structures of [Fe(H2O)6](BF4)2, (Ba1.5Sr0.5)TiO4, and (Ba1.25Sr0.75)TiO4.

The crystal structure of the mullite in a commercial material was refined by the Rietveld method using laboratory X-ray powder diffraction data. In this one refinement, most of the common challenges—including variable stoichiometry (partially occupied sites), multiple impurity phases, amorphous material, constraints, restraints, correlation, anisotropic profiles, microabsorption, and contamination during grinding—are encountered and the thought processes during the refinement are described step-by-step. Interpretation of the refinements includes bulk chemical analysis, chemical composition of the mullite, assessment of the geometry, bond valence sums, the displacement coefficients, crystallite size and microstrain, comparison to similar structures to assess chemical reasonableness, and the nature of the amorphous phase.

The restrained (air bag and seatbelt) driver of a vehicle involved in a high-speed motor-vehicle accident sustained a tear of the thoracic aorta with no signs of external injury. Air bag deployment may mask significant internal injury, and a high index of suspicion is warranted in such situations.