Good piece in the Sunday LAT that began as a post on Jill Leovy's Homicide Report blog: LAPD officers frequently assign the wrong name to Latino crime victims and arrestees. Partly it's due to the limitations of the standard LAPD form, and partly due to officer indifference or training.
The LAPD's most basic arrest form — the "5.10" — is designed according to English name conventions. It provides spaces for "last name, first name, middle name," a format that all but guarantees a Spanish name will be botched, because it won't fit into the spaces.
The department says it trains around this issue. But not surprisingly, officers queried in the field described making it up as they go along. Some said they hyphenate Spanish-speakers' names. Some said they use one or the other last name. Some said they put one of the last names in the "middle name" slot.
Often, extra last names end up filed as aliases. This means that even if people aren't lying to police about who they are, their police records will carry a whiff of shadiness because it appears that they adopted fictitious names.
I would find the Homicide Blog a more compelling read (and more useful to LAO) if entries were date-stamped on the main page and had more obvious permalinks.