Your forensic approach to the Nephilim is crucial, as this subject is often obscured by speculation. The biblical evidence provides a clear though limited picture.

**Genesis 6:1-4 Core Text:**
"When men began to multiply on the face of the earth...the sons of God saw the daughters of men that they were beautiful; and they took wives for themselves of all whom they chose...There were giants on the earth in those days, and also afterward, when the sons of God came in to the daughters of men and they bore children to them. Those were the mighty men who were of old, men of renown."

**Key Terms Forensic Analysis:**

**"Sons of God" (בְּנֵי הָאֱלֹהִים - bene ha'elohim):**
- Job 1:6: "sons of God came to present themselves before the Lord" - clearly angelic beings
- Job 38:7: "the morning stars sang together, and all the sons of God shouted for joy" - creation context
- Always refers to angelic beings in Hebrew Scriptures
- No biblical instance where "sons of God" means righteous human line

**"Daughters of Men" (בְּנֹות הָאָדָם - benot ha'adam):**
- Standard term for human women
- Contrasts divine/angelic beings with humanity

**Nephilim (נְפִילִים):**
- From root naphal - "to fall"
- Often translated "giants" but literally "fallen ones"
- May indicate both physical size and moral/spiritual fallen nature

**Post-Flood Nephilim Evidence:**
- Numbers 13:33: "We saw the Nephilim there...and we were like grasshoppers"
- Deuteronomy 2:10-11: "Emim...accounted as Nephilim"
- Deuteronomy 3:11: King Og's bed 13 feet long
- Joshua 15:14: Caleb drove out three sons of Anak (giant clan)

**New Testament Corroboration:**
- 2 Peter 2:4-5: "God did not spare angels who sinned...bringing flood on world of ungodly"
- Jude 6: "Angels who did not keep their proper domain...chained in darkness"
- Both connect angelic sin with Flood judgment

**The Sin Nature:**
- Genesis 6:5: "Every intent of the thoughts of his heart was only evil continually"
- The hybrid offspring corrupted humanity's genetic line
- Required Flood to preserve human purity

**Forensic Conclusions:**
1. "Sons of God" = angelic beings (not Sethites)
2. Union produced hybrid Nephilim giants
3. This genetic corruption necessitated the Flood
4. Some Nephilim bloodline survived through Ham's wife (?)
5. Post-Flood giants were remnants of this corrupted line

**Contrary Theories Refuted:**
- Sethite view (sons of Seth vs daughters of Cain) lacks textual support
- No evidence "sons of God" ever means righteous humans in Hebrew
- Angelic interpretation fits immediate context and ancient understanding

The evidence consistently points to angelic beings crossing created boundaries to corrupt humanity, resulting in hybrid offspring that threatened human existence and purity. This understanding aligns with the Flood's necessity and explains the post-Flood giant references.