If US homicide data would be of interest to you, I would recommend a couple of sources:
For general data, the FBI’s Uniform Crime Report website or the CDC’s National Center for Health Statistics website provide overall numbers, and some basic demographics about victims and offenders:
CDC Health Statistics - Assault or Homicide (2014): https://www.cdc.gov/nchs/fastats/homicide.htm
For detailed information regarding the circumstances surrounding homicides and factors presented by offenders, I would recommend requesting data access through the CDC’s National Violent Death Reporting System:
The National Violent Death Reporting System (NVDRS) is a US program, which collects data on the circumstances surrounding violent deaths from a majority of states around the country. It also collects information on the victim and the offender, including important and often missed psychological data. The data comes directly from state abstractors, who review coroner, autopsy, and law enforcement reports to generate a thorough picture of the violent death and the factors that led to it.
There is no fee for data use, though you will have to complete an application, and receive subsequent approval by the CDC to access the data. While this may take some time, I can think of no better current data source that has such a complete list of variables applicable to your stated investigative interest(s).
I might also recommend two pieces of literature that could strengthen your theoretical framework:
Spinelli, M.G. (2004). Maternal infanticide associated with mental illness: prevention and the promise of saved lives. Am J Psychiatry, 161, pp. 1548-1557.
Ben-Noun (Nun), Liubov (2017). Neonaticide, infanticide, and filicide: Unique medical research in biblical times from the viewpoint of contemporary perspective.
Both of these works (along with their researchers, if I’m not mistaken) can be found right here on ResearchGate.
Infanticide can be found in a number of scholarly admitted articles that pertain to all subjects in correlation to said subject. I can supply you with a plethora of data (as I have studied the primal act to a high degree), as well being open to any data, questions, etc. you may need.